Southern England also doesn't afford the kind of convenient outdoor climbing that Southern California did

Indeed. There's the legendarily-terrible southern sandstone, but from what I hear, if you're going to have to travel, most people choose to head up to the Peak District or somewhere like that.

On the plus side, if you find a climbing wall you like, you'll often be able to connect with people there who are organizing trips to the great outdoors.

ETA: Forgot to say -- this looks like it might be a useful resource.