Well it seems as if overall you're not a massive fan of UCL - but then I felt exactly the same way about UEA and it was a really rainy day, I was stressed about exams and was generally peed off. I would recommend visiting it one more time - you're going to spend the next three years of your life there so it's worth checking it out.
You mentioned that UCL is better in terms of reputation for Archeology specifically. Overall, both uni's have a really good rep, so it depends if you're likely to go into reserach in archeology after your degree. If you do, then UCL could be better if it's more well known for that (I dont actually know, I'm just going on what you said!). But to be honest, both have a good rep so if you wanted to do reseach, either decision wouldn't do you any harm.
So in my opinon, Bristol looks like a good option for you as you seem to prefer it! But check out UCL one more time just to make sure...