It's also worth remembering that in the UK you can still accrue AA miles quite easily:

AA eShopping just opened a UK portal: see
http://www.flyertalk.com/forum/showt...php?p=10185129

and Citibank UK offer a £ based credit card (albeit with 1mi/£ instead of 1mi/$ and a miserable 5k opening bonus, compared to the generous 25k bonuses they offer in the USA).

Just something to consider. Also remember that since you'll be travelling "internationally" on any OneWorld flight you take from the UK because it won't be in or originating from the USA, once you have AA PLT status (which you could get through a challenge in one TATL trip in business class), you'll be able to use the lounges and quick checkin when travelling BA, IB, AY, MA, RJ etc.

That said, if you're still set on a UK-based program, BMI seems the best one to my mind, but who knows when they'll be bought by LH and your miles will turn into Miles&Less?