BA is currently offering huge sale prices on a bunch of places. £299 to SF between certain dates.

http://www.britishairways.co.uk/travel/septemberoffer/public/en_gb

Fall and Spring are both excellent times to come to San Francisco. The fog isn’t as bad as it is in the summer, and its not too cold (not that it even is compared to the UK).

You may want to try United ( http://www.ual.com ) or American Airlines ( http://www.aa.com ). Sign up for their “e-fares”, I’ve seen last minute flights to London from San Francisco for $300 USD in the past. Also, flights from London to Los Angeles will almost certainly be cheaper given that there are more flights and competition. It’s only a 6 hour drive, and if you take your time and take the coastal route, it can be very spectacular…..also Southwest Airlines has <$120 round trips from LA if you book early enough (and you could fly into Oakland, San Francisco, or San Jose)....( http://www.southwest.com )

Ahah id say generally speaking as far as weather goes…its up to what you like. The winters out here are not that bad at all. Last winter it was a really…um..not too bad at all.Barely enough rain. Ahha. I myself prefer right now…its Fall. Cause in the summer..its hot for me..ahah. I just dont like the sun or the heat in any shape way or form. But def. come visit the area. Its beautiful no matter when you come…make sure to see those damned city lights at night my friend. And walk around the pier at night….beautiful.

I would say the best time of year to visit is late September or early October. You can luck out and get an indian summer. Also this time of year the fog doesn’t tend to roll in as much as it does during the summer. Plus you have the added bonus of it being crush in the wine country, which is always a fun thing to go see. Tickets also get a little cheaper as do hotels. Early spring is also not a bad time to come. I would just avoid summer because you can just get fogged in the whole time you are here.