Thanks guys. Boyfriend & I don't have enough UA miles (we're both US Air lifers), and the US flight home is moronically expensive - rather than him paying $3k to ride that flight with me, it's easier for me to waste points on the round trip and take a much cheaper flight back together on cash (and I have a feeling that suggesting we fly back separately from a romantic vacation to maximize points is NOT going to go over well).

Follow up - if I buy a round trip BOS-LHR-BOS, can I then refund the LHR-BOS (paying the $200 refund fee I'm guessing?) or reschedule it into a totally different domestic flight (say BOS-SFO, a couple months later... again the refund fee), or am I really just stuck throwing it out?