Return flights from New Zealand with Cathay at the weekend took me to Silver

. The BA site informed me I had qualified for silver this morning (impressive) but still shows me as Blue and won't let me make any free seat selections. Can anyone tell me how long it takes before the website will let me use my new status?
There will probably need to be some discussion to get my TPs from the second flight recredited (it was 2 days after the first leg) but armed with info from FT I hope that will not be too much hassle.