hi got no reverse .checked fluid and linkage serviced 12 months ago anyone had a problem like this ,I'm hoping its something simple but i think its history

Sorry to say this is a verry common problem. Sounds like the d/r clutch pack has burnt out either from low oil, over heating or just old piston seals. 3rd gear will also be slipping or will be very soon.
This auto would need a rebuild along with the torque converter and diff as the diff has seals wich separate the auto and diff oils. I would suggest to change the automatic heat exchange for a air to fluid trans cooler with a thermostat switch and fan.
Aaron

Tidy bus to buy the way!!

AAron is the auto expert

Nice looking bus!