Ha - you deleted it while I was reading
Anyway, probably the number is still on the
relevant BT databases as at your old address, so the order on BT by O2 will be being rejected due to incompatible addresses. And/or the number showing on them for that address is whatever it was before.
The BT databases usually take 3 or 4 days to update.
To change ISP, particularly if you can get O2 LLU at the new address (you didn't say) sounds like a frustration thought rather than a considered judgement.