Pix/thesilb -- there are actually only two UC reward seats on popular routes, including LHR-SFO. The only cases in which reward inventory are opened up are (a) when a V.Top or V.Gold asks nicely and (b) if seats are available close to departure and then only in rarely. If you are not a top tier VFC member and are flying at the weekend then there is little chance. Also, VS are protecting the premium nature of the Suites at the moment, which means UC is very difficult for reward purposes. Incidentally, the earliest I could get a pair of reward seats at weekend on this route was early September.
As a Gold FC member I have had reward inventory opened up from time to time, but usually for companion seats rather than pure reward tickets. Also, be aware that the reward inventory is handled by the Revenue Management team not Flying Club, so don't expect miracles.
BC