I cashed in American Airlines frequent flier miles for a First class ticket.

American Airlines -Austin, Chicago, Heathrow
British Airways - Heathrow, Nairobi
return

British Airways - Nairobi, Heathrow, Toronto,
American Airlines - Toronto, Chicago, Austin.


I arrive to Heathrow at like 10:30 pm and leave the next day for Nairobi at abou 11am.

On the way back I arrive into Heathrow at 5am and leave around 11am.

My main question is around if I can reserve the concorde cabana rather than getting a hotel room on the way to Nairobi and possibly on the way back.

Can you pre-book spa treatments?

Any other suggestions to get the most out of my first class experience?