I generally commute between LHR and SFO. I'm fine with Economy on the way out, as long as I've carefully chosen my seat to give extra legroom and/or a bulkhead, or I have an entire row to myself. I really don't need any more. However, it has to be Business on the way back. I managed that every time last year, with only one booked Business trip - the others were all booked Economy. The trick, which will come as a shock on this particular Forum, is to use UA rather than BA - the annual six free upgrades plus a couple of other tricks go straight into C - and there a fair number of decent economy seats to choose from.