Hi I’ve just bought a discovery 4 12000 miles. I’m going to have a new cam belt fitted , but one garage is saying I also need the fuel belt changed too. Another garage is saying I don’t as it at the back of the car, they said you you change it on the discovery 3 when changing a cam belt but not the 4 . Am confused can someone please advise me on what to do?

As the D3 and D4 engine are essentially the same engine, then I can't see why the belt change intervals would be different.
Garages don't like doing the fuel pump belt because it's a pain to do.