Pulsacoil 2000 tripping out & wiring query

I am trying to sort out a problem for a friend.
The RCD is tripping out after a random period of time.
The wiring appears to differ from the manual in that there are red wires in terminal 11 and the spur attached to terminals 8, 9 & 10 appears inactive.
I would appreciate your advice
Best regards
Jon

I've now contacted the official technical agent (60p per minute).
They advise that it could be either
a) the thermostat or
b) the relay or isolating terminal connection or
c) the immersion heater element
Further investigation required..............

Make sure they check the mains electrics as well. I don't think Gledhill work on mains so confirm with whoever you use that they are also qualified to work on domestic electrical installations.