Any ideas
 

I was driving on the M25 yesterday when it started raining so I switched on my windscreen wipers, The rain got heavier and suddenly the wipers stopped and the interior courtesy light came on. I switched off the wipers and when I tried to restart them the courtesy light would shine and the wipers would be stopped. Luckily for me the rain stopped and I was able to continue my journey home, just before I got home I tried the wipers again and they started working normally - a strange one.

Earth , water ingress .

Check the plenum drain.

Plenum is fine it must be an earth, my son mentioned this when I asked him

Both the wipers and interior lights are controlled by the Body Control Unit.

As Mike Noc has pointed out both reliant upon BCU, I’d be checking there for possible ingress.
Mick

Thank you guys re BCU, I have purchased a second-hand one but I believe they have to be T4 installed, Is that correct or can I just try the new second-hand one.

think t4 would be required but also may be able to do it with TOAF program as toaf can read the bcu, add keys etc.