I haven't seen a £399 upgrade on a TA (amex) fare at online checking, but was offered it at T5 airside once (equipment change meant I was separated from a collegue on a separate PNR and were were asking what could be done).

That was a fairly full flight to PEK (one with Willie Walsh onboard, not in W I hasten to add!)

I flew BA264 (the 767) in May and there was no upgrade availability at checkin. As it's a sleeper service in CW, there was no food in the lounge, and my fellow W-ers feeding requirements meant the cabin was only quiet for about 4 hours, not nice with a full days work to look forward too.