Rob, welcome to the logical way this fault seems to manifest ! 😞
Only thing I can suggest is try dropping the roof to see if you can see any damage to the Motor ECU, I.e Water ingress ? You said your car was laid up for a couple of weeks ? Was it in a wet environment ? they do seem to be very fragile to any sort of change. Humidity or Battery.
Update to all on my Issue.
Ordered a new part from UAE cost approx £600 and was shipped really quickly, arrived and fitted all working now ! Phew !! what a mess It seems like if you have a RX450H 2010 model, this is an issue you will come across some time or later.
I really cannot understand why these units seem to prone to a similar issues on the same car and same year and how we communicate this back to Lexus ?-
As for the detail I still don't know which actual item failed to cause this issue - as you need to change out the whole unit to fix when I suspect half of the mechanicals and motor are fine.
Thanks to all the people on here that helped in this and good advice was given to narrow down my fault.
Paul