For an inexpensive, unique and quirky stay not far from Temple Meads and the city centre, I don't think you could find much better than Towed Town Camping. While it may initially seem like "some caravans in a warehouse" would be a ridiculous idea for accommodation, it was all done very well, and really did give the vibe of a small campsite indoors! The amenities were great, there was a lot to do in the campsite itself, with an excellent DVD and boardgame collection as well as ping-pong and pool, and the caravan I stayed in was wonderfully warm and comfy all night. I only stayed for a night but I would have loved to stay for longer, and I definitely know where I'll be looking at first if I come to Bristol again!