Duma said:
There's no really worthwhile bouldering within 45 mins of Bristol...local interest only.
Much as it pains me to say it this is pretty accurate. If you want to go bouldering prepare for some esoterica.
Ladye Bay has some fun problems but the landings aren't the best and the rock can be a bit soft in places. Can be good for a sunny evening though.
Bathford/Sally in the Woods has quite a few bits and pieces, some of which are even pretty good! Combine harvester boulder is the main event. Not much hard stuff unless you like roof crack based link ups.
Crosscombe is also good but probably a bit far unless you're based in the very south of Bristol and/or are happy to get up a bit early.
Cheddar has some good bits and pieces dotted around. Tombstone is the main event, there's a few lines in the same cave to mix it up. It can suffer from seepage though so probably want to try and get a conditions report if you're going to go there.
Meds Cave is pretty much in cheddar too. Personally I really like it (as a limestone cave with <10 lines, anyway) but others hate it. There's an excellent topo floating around somewhere (where excellent = weird, funny, slightly disturbing).
Brean Down has a couple of fun traverses and is generally pretty sunny. Excellent views of the mud flats and static caravans.
Gollums cave all the worst bits of parisellas without any of the good bits. Added crack heads to keep it interesting. It does stay pretty dry though, and the views down the gorge are pretty good.
Avon Gorge has a smattering of problems around the sea walls area as well as a few short routes which can be highballed.
ed: reviews for some of the ones you linked above.
Ring road boulders pretty limited would be a generous description. Nice rock but very few actual lines and very many eliminates.
Bourton combe home of the low ball eliminate traverse, though if that's your bag there's a lot of choice (i.e. there's a lot of holds on the traverse, many of which can be eliminated)
Snuff mills/frome valley sandstone good for some sketchy highballing. Purist esoterica.
Winterbourne down kind of frome valley but worth mentioning separately as it's actually pretty good for some highballing. Nice spot by a river.