Further to my problems I think it's time for some advanced diagnostics.
*fully charged battery
*power at ignition switch and at terminal with ignition switched on
* no power at seat micro switch or brake micro switch or blade engage switch
*motor will start and run if jumped started directly to starter motor and with earth lead (cut out earth lead) disconnected
*blades will engage and turn
*cannot drive either forward or reverse although main flywheel is turning.
*motor stalls if flywheel blocked - therefore key not broken

In summary,
- no electrics past ignition switch - is this damaged? why after stalling on rocks?
- is there a transmission problem as main crankshaft spins as does belt but no drive

Any help appreciated