Hi Dave, I am having snags with my left sliding door. It's got me stumped.
The sliding door ecu is behind the rear right hand trim panel just above the wheel arch.
There is also a sliding door cut-off unit situated just forward of the ecu which may cause problems. There are 2 large 40A Maxi-fuses in the battery compartment, maybe worth pulling them and re-inserting. Sometimes works, but not for me.
Good luck with your fault finding. If you discover it is definitely the ECU I have one for sale on eBay for £100 or best offer.