I cant give you much info about the uni's themselves but I can tell you a bit about the areas.
University of Westminster is within London, which is very different from the rest of the UK, for one its incredibly expensive, if you're getting student loans they'll be increased to compensate but you will still struggle more than if you were anywhere else.
London has a lot of "culture" around young people, lots of clubs and lots of variety within this. It's also a VERY multicultural city, thats a pro or con depending on how you feel about it.
Bournemouth is a bit more rural, there'll still be nightlife because there's always nightlife around a university, but the town itself will be a lot smaller, and you'll be a lot more limited in terms of your option of things to do. It's by the sea though, so that's nice.
And I dont blame you for not trusting the student room, they're a bunch of cunts. I'd suggest posting on 4chans britfeel thread asking about this too, it's usually up on the /r9k/ board. We dont like they're thread culture much (hence us not being there) but they do have a LOT more traffic than us, and could probably answer you better simply because of the variety of people.
It might also be worth what youre looking to do at uni, what you study could determine quality of the uni itself (just because somewhere has a good maths department, doesnt mean the same sort of funding goes to history) It's also worth checking out the societies at the uni, which you can probably find by googling X uni societies. This will at least give you a look at if you'll find people sharing your hobbies easily.