If you are doing Zoo, Zoo Project on a Saturday does be better than Channel Zoo on Wednesday, so everybody I spoke to says.
Space is good. Carl Cox on Tuesdays, ENTER on Thursdays & We Love Sundays are probably the biggest nights but you have Roger Sanchez on Mondays, Ibiza Calling on Wednesdays, so you may find something to suit your taste, although I would recommend Carl Cox
Cream's main room is trance orientated with the likes of Paul Van Dyke. It does be quite busy too, just a heads up. They actually over sold the day I went.
If you like Trance, I got into Full On Ferry for free, so give it a shot. Not sure about bars near West End because I didn't visit them much. Been to The Highlander (Scottish, good crowd), Ground Zero (Indie, quite sweaty), Play2 (Decent house music & open late), Plastik (Was there for Hed Kandi pre party).
I agree with above on Sankeys for a more underground scene though. However, it's quite deep house/tech house orientated which may not suit you.
As for Ocean Beach, if you have nothing to do on 1 day, it's quite cheap entry if you wanted to check it out. I never did, but might when I go back.