LHR-YVR(BA) does earn Aadvantage miles whle LHR-SFO does not. ANC service ends sometime in September (last year was first week of Sept, haven't checked the timetable for this year, but presumably you have already checked for your dates). Not sure if the OWE rules have been revised yet to include IST in the middle east (if they have, you can't combine it with DXB; the old rules did allow IST). An alternative to IST is HEL. You may have trouble getting CX on HKG-LHR, that route has been running fully booked in F most days. BA usually has space when CX does not.