I am not saying the garage are wrong but if you have a leak form the thermostat it may not actually be the thermostat itself. When I had that on mine it was just one of the horrible wire clips had rusted through behind the pipe where you couldn't...
A thermostat is an easy job mate. £350? Pullin the wool mate. I have a 300 tdi so don’t know much bout td5 but it can’t be too different to change out. Identify where it is and drain off the coolant a bit then undo housing to access the...