If you have a functioning IB account it will offer you PMI-LHR at their higher rate (11250 + $18).
AAdvantage will show some indirect AB/BA options via BSL/ZRH/DUS/FRA (but no obvious Band 1+1 options). There is also, from their map, some availability back from MIL/GVA/STR/BRU/AMS/PAR but nothing that stands out.