I'd be fairly suspicious about UK gyms because MMA has shot up so considerably in recent years due to recent expansion. While the US has had many mixed academies since long before the TUF boom, the UK hasn't had many famed gyms or MMArtists until Bisping. Maybe I'm stereotyping here, but I'd definitely be worried about McDojos trying to capitalize on the UK MMA fad.
And just as an update, I ended up training at the place for a month, and was fairly happy with the instructing, but ended up not continuing due to generally bad chemistry with the members and not enough money/time to make the training consistent.