All sorted.
Once the wishbone was removed there were two hidden screws that were securing the axle. All replaced with a spare and trolley working again :)
The right half of the axle on my S1 has sheared off from the gearbox. I need to replace the entire axle and gearbox and although I've uncoupled the motor and removed all of the screws that I can see I cannot actually get the axle off the main body of the trolley.
Has anyone replaced the axle...