Hi smith,
bmi are abandoning the carribean and usa routes from March as they they are moving from MAN to LHR and using the aircraft to Cairo and Amman.
You will probably have to phone the call centre to book.
For tips on booking there is a large thread on the bmi diamond club section of Flyertalk;
http://www.flyertalk.com/forum/bmi-diamond-club-486/
Good luck!
Regards
TBS