In reply to samben6:
Given some of the utter shite that has been developed in N Bristol, I'd give the undeveloped stuff a miss!
On a more serious note, developing a sport crag (which sounds like what you are after) is a much more complex proposition than trad or boulder, I would advise against it unless you really know what you're doing.
There's some fun little sport routes plus a handful of trad in Blaise Estate, and you may also enjoy the ring road boulders.