Hopefully someone who uses lounges and has passed through NBO since the beginning of October, when the latest changes were made to post-fire operations, will be along.
i don't use lounges, a bar is enough for me but as I understand it BA's lounge was in the central multi-storey block, this was above the Arrivals terminal and was thus destroyed by the fire.
There is a second issue, just before the fire there was a contractual dispute between the company that had a monopoly of all duty free shops at all Kenyan airports, and that also operated the lounges. In this dispute all the company's staff were ejected from the airport, and the goods from the shops removed and dumped in the car park . I don't know if the operation of the lounges was affected by this, if it was they may not have been operating even before the fire.
KAA is currently advertising Invitations To Tender for the operation of shops and lounges at the airport, I don't know if there is some sort of temporary arrangement in place for the non-airline specific 'pay to use' lounges in the mean time.
If you are travelling business / first class, you would expect a decent airline to have made alternative arrangements for it's premium customers but it is BA you are flying with ヅ