My travel tip for Bristol is get there by Megabus if you're going from London. It'll almost certainly cost you a fifth or less than the train. It's probably cheaper from elsewhere as well. 
And bring decent shoes if you're planning to go anywhere without a car. The hills are immense. 
And, uh, don't hang around on the Downs on your own. Noooot good. 

Chav city....visit Newport if needs be but highly recommended to stay out of Pill....other than Ladbrokes and the occassional corner store there really isn't anything here for you!!