I agree with 'super', this is now definitely looking like my CPU/control board (and hence these roms) came from the ride-on version. I hadn't looked through the service menu completely before but now that I go into the INPUT TEST I see there's two extra settings for FOOT SW.R and FOOT SW.L. These settings are not in the hangon/hangon1 sets.
I've PM'ed a member on the J+ forums who may have a ride-on version, if he has and can photograph the board set for us, then it may well prove conclusive. He may also be able to dump the remaining missing roms from the sprite board and sound board to make this a full set.
This may also explain why my boardset has got an oily/greasy residue over certain part of it, maybe the oil/grease came from the hydraulics of the moving bike cabinet.