Can I Put puddle lights into my mirror casing, as I Would Like To fit them if possible? Car is mk3 VRS Pfl. Just wondered if the wiring was already there. 

Yes. I did mine but bought thr powerfold mirrors and new door modules from eBay.

 

It's a case of a straight swap and then code using OBDeleven.

If you don’t want to change the door controllers you can wire them into the door interior light feed

@SashaGrace's suggestion is considerably cheaper, especially if you're not fussed for folding mirrors!