I only started at the beginning of this month, but for anyone wanting to, or thinking of applying to BBK, here's what I can share so far:
Well for starters, I never attended the orientation (I had undergrad finals elsewhere to prepare for before beginning at London), but in all honesty it isn't hard to find your way around. Maps are available online and people (staff and students) are happy to help you find your way.
As far as the range of people attending (at least my course, BSc biomedicine) it is a diverse group, ethnically, age-wise, and roughly a 50/50 split in gender. Everyone has various academic backgrounds. For example I am a grammar school student and graduate, there are older grads, people with few formal qualifications, young post- A-level students, people educated abroad, etc. I haven't detected any snobbery or elitism from anyone I have met - indeed everyone seems keen to get to know each other and help each other whether they have previously met or not. There's also no seeming evidence of inferiority felt by others either.
Our classes are split between different colleges around the Bloomsbury area, and this doesn't have much effect on the students. Most seem pretty motivated, as you'd expect from a part-time group who have other pressures taking up most of their time (the reason I chose BBK over UCL full-time is due to other life commitments).
For the younger students thinking about BBK - you fears are ungrounded, I'm happy to say. Whilst most people drawn to part-time study are going to be older, they're not much older (I'm still in my 20s... ok very, very late 20s...), but even though there are differences you'll find that there being a common ground with the groups (i.e. the subjects) ties you all in together. University is much different from school!
As far as prestige is concerned... This isn't my first time at university, and I have to say the quality of teaching and work is pretty much what you'd expect from any college at the University of London - indeed we share facilities with other colleges, such as UCL and Kings, and this is not by coincidence. Make no bones about it, if you slack off just like any of their other colleges you will be kept under the watchful eye to ensure you really deserve or are able to keep pace with a UoL place.
I think the 'lack of prestige' label really comes from the numbers of students who do not have great academic backgrounds before studying at BBK. Nonetheless, the education offered is not compromised here, although I suspect drop out rates may be slightly higher because of this and the fact some older students may have trouble getting back into the swing of studying again, life commitments get in the way, or maybe they realised they simply didn't want to continue after all.
So in a nutshell:
You're studying at UoL which is no bad thing.
You have the benefit of close ties with students of other colleges, and people from diverse backgrounds.
It is part-time for the most part, enabling you to hold down commitments elsewhere (like I said before, this was the deciding factor to me).
Elitism is only for those who care about it - Studying at BBK instead of Imperial or Cambridge won't affect your passion to learn or intelligence, unless there are issues there anyway.
There's a good mix of those with few formal qualifications and advanced qualifications.
There are lots of extra-curricular activities (for want of a better phrase) open to you.
For those interested in humanities subjects, you have the benefit of studying in the heart of one of the great capital cities of the world - there is a lot to experience there!
BBK has some world-ranked departments, and links with Nobel laureates.
The people are friendly and helpful, and for the most part great to be around