there are American ships that call in at Californian ports of course (on their way to Alaska or the Panama canal or Hawaii) but I don't think many British based ones do. There are plenty of cruising websites (always aim at paying about half the brochure price), but I can't give any personal experiences on this route
Celebrity do a great one called 'the West coast wine cruise' cruise!. A leisurely tour down the West coast from Vancouver. Oct 13th this year and Oct 12th next year.
I suggest you check out celebritycruises.com site for more info. And before you go on any cruise the ONLY website to check is boars.cruisecritic.com. You will get tons of info regarding ships, ports etc there.