OP here. The problem was not that the BA system had not promoted me in time, it was that BA messed something up. BA has clearly admitted they messed up. Ironically my status is now Silver in the system (so it took 48 hours to update, which is a shame as 48 hours from original flights would have been weeks of spare time)

Had BA not messed something up, everything would have been fine.

so @nux- I should have been Silver by May 21-25th at the latest, per "few days." I totally get things are not instantaneous, looks like 48 hours...

@Guy Betsy I think BA owes me something, but I want evidence that what I say happened actually happened. Per your other point I DID have a letter saying I was silver on BA, and CX did refuse to accomodate me, why shouldn't they acknowledge that? And to your other point about mingling- mingling at midnight, when everything in airport is shut was no fun. What's the point of status if you don't get lounge access etc.

@Dave Noble- what you say is what I expected, hence why I got the letter from BA, but I would think that clear evidence of status ought to be enough, I don't see why a customer focused business should operate on the basis of "The System" dominating.

Thanks all for your feedback. All very "first world problem" but I will see what BA proposes to do to say sorry (sound of not holding breath)