Have you been able to visit either of the places? UCL is in the central part of London, nice but very very busy and accomodation will be ridiculously expensive.
I have friends who went to reading and they enjoyed it a lot, and same with UCL. Henley is an absolutely lovely place to live! Its considerably smaller than London, and every year hosts the Henley Regatta, so its not some boring place. It is a bit outside of actual Reading though, but has everything you need (i.e. shops and the like).
Judging by the fact Reading is better with those types of courses, you'll probably benefit more from going there, as the teaching may be better. If possible and you haven't, try and visit both places and see what you prefer! Sorry I can't be of more help