Quickly plugging those figures into Parcel2Go shows TNT will be £54.40, but that's from a business address. FedEx will do it for £60.
As for the C64 - It would be a bit silly to have a repair service where the customer needed to know what was wrong.

The usual entire diagnosis I get when sent a C64 for repair "The screen's black"... therefore I have ways to find out what's actually wrong - some of which are even more technical than "put finger on RAM chip and see if it burns your finger off", which is always the place to start when diagnosing a C64.
So no, person sends me C64 which is kaput, and I send them same C64 which now works.