Thanks number_6 and JGR01 - that sets my mind at rest and is good to know for the future - we're planning a holiday to Orlando/Miami for a couple of weeks ending in Miami during Superbowl weekend (we must be crazy!) - I guess there's sod all chance of getting 17AB or 17HJ on the MAN-ORD flight (crew rest).
We flew MAN-MIA and back in November/December 2004 on a 767-300 - requested a move from 31AB to 10HJ on outbound at gate. I'll not mention the op-up on the way back (courtesy of late arriving cruise ship and massive overselling in Y!)