Originally Posted by
UKtravelbear
For 2k miles (per seat) you could get a miles+money fare in economy. It will give you a small discount off the normal fare (which you could then use to buy an extra leg room or exit row seat) but you won't earn any more miles or tier points for the flight.
Considering that you would be giving up earning 5,000 or so miles for an economy SFO-LHR, you have to be really careful about miles & money. If you want to get rid of a few miles, fair enough, but otherwise I think you're much better slowly and surely working your way up to at least a 1-way long haul or domestic US redemption...