Unfortunately the UK isn't exactly... known for world-renowned legendary earth-beating roller coasters but I can probably help in finding something close.
The ones that are closest to the euphoric paradise that you're looking for, on this island, are...
Megafobia at Oakwood is the largest wooden coaster in the UK, located in southern Wales. Recently retracked to provide significantly more airtime.
Smiler at Alton Towers is the roller coaster with the most inversions in the world.
Stealth at Thorpe Park is one of the fastest accelerations on any roller coaster, reaching 80mph in less than two seconds.
Icon at Blackpool Pleasure Beach isn't very intense, but is one of the most outright fun and rerideable coasters in the UK.
Big One at Blackpool Pleasure Beach for, erm, obvious reasons. It's big, it's fast, its first drop in the back seat tries to kill you.
Those are the top 5 for me personally, but there's a few more that I'd like to mention:
Saw - The Ride at Thorpe Park for its horror themed aesthetic.
Oblivion at Alton Towers is a short but incredible drop into a complete abyss. Nothing else like it.
Revolution at Blackpool Pleasure Beach may not look like much, but its backwards loop is a genuine contender for the most intense bit on any roller coaster in the UK.
Odyssey at Fantasy Island is a cartoonishly big inverted roller coaster, one of the largest rides of its type.
Shockwave at Drayton Manor has the only stand-up Zero G Roll inversion in the world.
Unfortunately most (but not all) of the roller coasters on this list have a reputation for being a rough and not-smooth ride, but hopefully you are able to find a smooth seat.
I also want to recommend some insane non-coaster thrill rides:
Aerospace at Barry Island Pleasure Park is the tallest ride in the UK, a truly astonishing height of over 60 meters that you get to experience completely upside down.
Vertigo at Oakwood and SkyCoaster at Blackpool's South Pier have you soaring over hundreds of feet in the air suspended by nothing but a cable.
Time Machine at Adventure Island is perhaps the most dizzying & unique ride in the continent, a completely custom-built thrill ride that feels like it was designed to send you into the dizzy dimension.