Thanks for your help, back wiper is working. Uncles Gona replace the micro switch first, when he opened it up a part of it had broken, fingers crossed that might resolve it 🤞
Be prepared for a shock, the microswitch only comes as part of the rear trim that sits above the number plate. Costs about £130 + vat for the unpainted one.
And that switch is uniqe to the DS4, you can but one for the C4 (and other peugeots) extremely cheaply, but it's different.
Mine was the same, the microswitch behaved funny when it was on the way out. Random boot opening or not opening. Having to quickly shut the boot and start the car to keep it shut as the boot wont open with the car running.