200Tdi will not start with key, have to arc starter

Hi to all, helped me uncle out yesterday changing starter motor on his K reg 200tdi all went well..... unitl we tried to fire her up, just heard clicking from the relays under foot panal (drivers side) when turning the key, tried starter motor (arc with a spanner) started fine,

Is there a starter relay?
Where is the damm thing?
If not, what could it be?

Thanks to all that read & post greatly apreciated

solenoid on starter,take wire off solenoid and see if live while someone turns key to start position,if it is live check solenoid ,if not work back to relay

The relay is in the passenger foot well (Yellow). If it still does not go try pushing a small wire into the relay block (and push in relay to secure it)in the hole where the large red wire goes into the back then attach the other end to the starter solenoid. If it now starts on the key it could be a fuseable link,and you have just wired around it!