Well, it actually happened!

Thanks BA for upgrading my twin sister and I to CW (from WT+ - LHR-JFK). We checked in at the CW desk (abusing my Silver status as the "fast" bag drop wasn't...) and the check in assistant made a quiet phone call (couldn't hear what she was saying), ripped up my pre-printed boarding pass and issued us with J BPs instead.

I was completely surprised. My sister has never flown business in any airline so she was suitably impressed too. She is, needless to say, a BA convert!

It was totally unexpected and really appreciated - I've been flying BA a couple of years and never expected to get an op-up. It was the nicest possible start to the trip...

Thanks BA! And thanks to you folks for the invaluable info you share. I've learned a great deal.