DL2506

I have a MK1-TT, APX engine code. Car has recently developed a fault where it will not start. Mechanic friend feels that a main relay has failed, being that he is getting no reading at all from ECU to his code reader, and being that the fuel pump cannot be heard priming on key turn. All fuses (even ones on top of battery) have been checked and are ok.

Does anyone know where this relay is physically located and whether it has a colour or number code? No doubt it's located somewhere behind the dash?

Many thanks in advance.
D.