BA still has some pretty attractive fares, though you may need to go out of LGW to get them. I priced Sept 14-19 on aa.com as sample dates and the base fare was $83 ($127 with taxes). I'd hold onto the miles if you can find fares for your dates in that price range (or lower). Using Aer Lingus out of LHR showed a $121 base fare for the same dates ($181 with taxes).