AOW isn't advanced; it's additional. To get you on the boats it's a good thing. We get this dahn sarf as well (Brighton-ish); the OW people are restricted pretty much to drift dives. You're rather caught in a quandry; until you've selected your club, you don't know which agency to go with. Personally I'd consider doing the AOW anyway, just to get it out of the way. Then if you're ending up with BSAC, you'll just go in on the Sports Diver sylabus and re-do some of the skills (and there's nothing wrong with that!). With UK diving, you really do need to be able to dive to 30 metres and be pretty comfortable in low-vis conditions which can suddenly happen if someone kicks up the bottom. More importantly you don't want to be too dependent on your buddies and be able to happily ascend on your own with an SMB. Tip: always volunteer to put the blob up.