Have 2 weeks touring SF area in September, then want to fly to LV for 3 nights before returning to the UK - best to book this flight in advance here in the UK (have been quoted £52) from SF to LV, or best to book once in the States? Thanks everyone.

Probably better to book before you leave home. The main reason is that the better deals tend to be for advanced purchase - the closer to flight date the less the chance of getting a discounted fare.

You check airline US websites to see if you get a different rate (Southwest, United, America West, etc)

J62 is correct about advance purchase tickets. I recommend checking Southwest Airlines in addition to the other carriers. You will not find SW on orbitz, expedia, etc., so you must go directly to thier web page at:

www.southwest.com

Southwest doesn't fly LAS to SFO non-stop, but they do fly to Oakland and San Jose, both of which are in the greater SF area, as well as Sacramento if you're further afoot from SF in your travels.

J

Book in advance but wait until July when the sale fares start popping up.

Contact your transatlantic carrier and ask about an open jaw itinerary - UK to SF, LV to UK. That way you may only need one way transport between the Bay Area and LV.

Still, £52 (if that's a return fare) is pretty good, and with rising fuel prices I'd probably just book it now and move on to other matters in planning your holiday.