Posted: Wed Feb 27, 2019 9:11am
What are you calling a "paper licence"?
If you're referring to the now defunct paper counterpart to the UK photocard then although it's (still) widely believed otherwise of itself that is NOT a licence and cannot be used to drive with anywhere.
Whichever type of licence you hold though at this late hour in the Brexit fiasco and with the threat that in a no deal scenario a UK licence may cease to be exchangeable for a Spanish one forcing you to take a Spanish test, the idea of delaying an exchange for the sake of what presumably would be an optional 'holiday' in UK, seems rather ill advised.
Note in UK at least there is no obligation to carry your licence when driving so if you did initiate a exchange and decided to make the trip back armed only with a slip of paper from trafico (and taking the ferry from Spain) then if stopped in UK you'd probably be ok claiming that you'd lost or misplaced your licence as a police roadside check with DVLA will - or ought to - establish your entitlement to be driving.
Personally I don't think I'd risk it though!