I did originally want to use DPD as they're who I trust the most but I've looked into their prices and for any parcel that's above £50 it's.... expensive. So Royal Mail it is.

I gave their customer services a call just now and they say there's no reason why they wouldn't pay out if the label was generated through eBay so I think I'll be okay. SD is very annoying but what everyone's telling me is much more of an inconvenience.

Appreciate the help mate, enjoy your Sunday