I don't know if you've made your decision yet, but I'm studying at Hertfordshire at the moment, and the place is a dump...
Well, the university's ok, but the Hatfield area is chavtastically awful. On the plus side though, Hatfield station is 25 minutes away from Kings Cross.
The Business School campus (de Havilland) has excellent sports facilities, a student bar (which I've never been into), far superior halls of residence (ensuite + personal fridge), a good cafeteria and fairly large library, and is also where the International Office is located. However, with the opening of a Law School on the same campus last year, the place is now horribly overcrowded, and prices for food/drink/accommodation is fairly ludicrous.
The main campus, College Lane, is a free shuttle bus trip away, and is the much larger campus containing mainly the same stuff as de Hav, but without the sports centre and with a three-story nightclub/winebar/cafeteria facility instead.
Teaching at both campus is mediocre at best and fluctuates wildly with whom's teaching you. By far the worst thing about the university is the intranet system they have in place called StudyNet. It's impossible to find anything on it, and once you do it's more than likely out of date, although it does have a good online library on it though.
So, yeah, it's in an awful area, and most of what you can find in Hertfordshire you can probably find executed much better at other universities.
You can easily get into London from there though, and don't worry about bumping into me at all because I'll hopefully be long gone by then.