I had my share of luck last night LHR-CPT. MMB showed me an upgrade from Y to W 48hours before the flight! RESULT!
Turning up at the gate they said - the flight is so busy that I now have a nice seat in J. I was travelling with a colleague - who's quite new to our company and it was her first BA flight and they extended the upgrade at the gate to her as well and upgraded her from Y all the way to J.

Thanks to BA and I did fille a welldone form for the CSD who was serving my aisle if CW and was just SUPERB throughout the flight.