This is a very interesting question, but hoo boy, it will take some time to answer properly. At least when I'm asked about it.
First, I think, the premise of the question warrants some exploration: what is B&M offering, that parks in Europe would be likely to build? I think the answer is related to why the question was asked in the first place: B&M's coasters all come in very big boxes. And they have a fairly limited selection too: the B&M home page lists only nine models for sale: Wing, Hyper, Dive, Flying, Floorless, Inverted, Sitting, Stand-up, and Family coasters - the latter come both in inverted and non-inverted configurations, although nobody has bought the non-inverted ones yet. Actually, only Happy Valley has bought the inverted one too, and I don't consider them likely to show up on the European market any time soon given the stiff competition from other, cheaper manufacturers in that market segment.
One simple issue greatly disfavours B&M, sadly: Their coasters all tend to be in the upper size range of what a park is willing to build these days. As @JammyH
touched upon above, parks have a ton of compact coaster models to choose between. Launched shuttle and semi-shuttle coaster layouts have really taken off across the industry, while B&M has yet to adapt to the introduction of conventional launch coasters. The Dive and Wing coasters have too wide trains to function with a compact layout, and inherently need a lot of space. You only build those when you have money to burn.
Not to mention, all the competition against other manufacturers when talking about coasters in that size range. I'd almost say you could discount B&M's conventional multi-loopers completely given how there are so many other, cheaper, or more flexible manufacturers offering comparable products: Mack, Intamin, Vekoma, S&S, RMC to some degree, even Gerstlauer if you want to stretch definitions a little. I think there's a reason why B&M hasn't built a new, conventional multilooper in the West since Led Zeppelin in 2008 (and since then, only two Floorless loopers in India and Hong Kong - barring the two Hulk clones for Universal Studios, of course). Others simply build 'em better or cheaper.
Hypers were never a favoured coaster type in Europe - there are only six conventional hypers in total across all manufacturers: Shambhala, Silver Star, Big One, Expedition GeForce, that new one in Walibi Belgium, and Goliath. New Hypers are an extremely rare occurrence, and it almost seems like all the parks that could afford or be allowed to build them have got them already. And again there's competition: Intamin, Mack, and Vekoma all offer their take on the conventional Hypers. I can't even imagine what it would take for an European park to order a B&M Hyper these days.
That leaves us with four B&M models with a credible chance on the European market: Inverts, Dive Machines, Wing Coasters, and Flying coasters. At least there's little competition here, which is why those coasters make up such a great chunk of B&M's sales record in the past few years. For inverts, the only real competitor is Vekoma, but it seems like Vekoma focuses on smaller-scale inverts than B&M. Intamin dabbles slightly in it as well, but with limited success so far (although both would probably outbid against B&M's family coaster model). Anyway, large-scale Inverts are kinda rare these days. Gröna Lund is actually the only park to have built a B&M Invert worldwide since Banshee (2014). The situation is almost the same for Dive Machines versus Eurofighters: for the small ones, go to Gerstlauer, for the big ones, go to B&M, and the two don't seem to compete against each other much. For Flyers, we have yet to see Vekoma's impact on that market segment, but it's kinda tiny already. Only 11 B&M Flyers have ever been built, and none outside Asia since 2009. I'm wondering if the parks see the Wing Coasters as a better alternative, by giving that same sensation of flying with much less hassle at the loading station. Anyway, since they are still built in Asia (at least until 2016, that's recent enough for me), let's not discount Flyers entirely.
So in conclusion (and oh my, we're only halfway yet), the question to answer is: "Which European parks could build a B&M Invert, Wing, Flyer or Dive Machine?".
In the UK, I could possibly see Thorpe get a Dive Machine à la Valkyria, or possibly a Flyer. They already have an Invert and a Wing, and appear to see great success with them, so future cooperation with B&M seems likely. I don't think a Hyper is likely, given the sheer amount of space and money required. Then again, Merlin's near-monopoly situation for thrill parks means they can keep investment to a minimum without losing market share, so a new expensive coaster at Thorpe may not happen for many years. No other park in the UK seems likely to be able to afford a B&M (money- and space-wise) in the foreseeable future, given the abundance of cheaper options and, dare I say it, a general tendency to flock towards those cheaper options whenever possible. Why build a new Manta clone when you can have a Pinfari Zyklon with only eight previous owners?
PortAventura with Ferrari Land is a wild card in Spain. Well, honestly, it's kind of the only card in Spain's deck. A little bit of RCDB-ing around provided a list to illustrate: That resort has built the only coasters in Spain to go faster than 80 km/h since 2006 (the year of Abismo - all other coasters to break that barrier in Spain were built in 2002 or before). But if they want to expand their portfolio a little, a B&M is not a bad call. They have two B&Ms already, yet none of the four discussed models.
It's always hard to tell with France. Tons of parks, all of them either kinda small or kinda uninterested in coasters, apart from Parc Asterix and Disneyland Paris. And with Disney being Disney, and Asterix having ordered a huge Intamin for 2022, the French market for big coasters appears to be saturated for the foreseeable future. But hey, you never know, suddenly some park we've never heard of with ten million annual visitors will order a family coaster to take guests around the medieval exhibit or something to that effect.
The German parks are unpredictable too, and likely candidates don't really stand out. Europa Park is Mack's domain. Phantasialand can't build tall (so no Dive Machine), have no space (so no Wing Coaster) and have all the Inverts and Flyers they need. Heide Park has an Invert, a Wing coaster, and a Dive Machine already, and Colossos might be big enough to cover the need for Hyper coasters too. But they could possibly get a Flyer? Maybe? The title of Europe's tallest Flyer is right there for the taking. Hansa Park could be another candidate. Movie Park Germany seems like the park that would have bought a B&M, but have to fight their owners to get funding for anything.
I don't see Denmark getting any B&M's any time soon. All their parks are family parks with family coasters aimed at families with kids coming by car from all over Scandinavia and northern Germany. Dæmonen is practically the biggest thrill coaster the country is likely to see, and that's at the very smallest size B&M builds. By extension, we could write off the rest of Scandinavia too. The Norwegian parks are too small, the Swedish ones too space-restricted.
Benelux? Maybe. Who knows. Toverland or Walibi Holland could have some plans. Walibi Belgium building that Hyper probably keeps them out of the market for a few years, but you never know what they will ask for when the coffers fill up again in a few years. Plopsaland is in the same situation, with that Mack spinner. Maybe the parks are big enough to want a B&M, but right now they have other plans.
Italy? Eh, you never know. Probably not Mirabilandia unless Parques Reunidos has a drastic change of philosophy/deservedly goes bust. Gardaland appears to have most of the B&M catalogue covered already. They have an Invert, a Wing, and a Dive Machine. That does leave a Flyer, theoretically, but Flyers are rare. I'm not sure if the other minor parks of Italy are big enough to afford B&M coasters, but you never know.
Poland? Hard to tell. Energylandia seems liable to build anything. There's also Legendia, but not much else. Likewise, most of central and eastern Europe seems to have too small parks for B&M to be an option. Maybe there are parks in Russia or Turkey that would order something. Those parks have a tendency to suddenly splurge on really big coasters after years of total quiet.
To conclude, it seems like @JammyH
has it right: B&M is outside the market for most parks, and they have many competitors for the contracts they can participate in. Big coasters are fairly rare, even at big parks, and B&M is one of many manufacturers to offer them. They have some niches, but do poorly outside of those. I wonder what would happen if the Chinese theme park market suddenly collapsed. Would B&M reform their conservative ways, and offer some smaller coasters, or remain steadfast to their principles as their contracts dwindle up? I guess we'll see. If B&M changes, the entire premise of this post may be turned completely on its head.
Whew, that was a long one.