Now then...RVSM is one thing all to do with height keeping and is not affected at all by the lack of an FMC...BRNAV is all to do with NAV and so is very affected by the lack of an FMC...
Top tips - Always know the power setting for the next phase of flight (approach - think G/A). Does the EGPWS terrain function need to be inhibited? Tell someone (ATC) if its going to help but shuddup if its going to hinder. Final tip - LOOK OUT OF THE WINDOW! It will of course just confirm that you are exactly where you expect to be!
BOAC - I am not going to say anything.....