Starter motor problems, relay 106?

[oscarbigfeet]

I've an 07, 2.0TDi Stylance with starter motor issues. Car developed a starting problem 6 months ago where the engine would turn over without starting, it would eventually start after 20-30 seconds of cranking. The longer this went on the more "tired" sounding the starter motor sounded and it was replaced back in the spring. The replacement "failed", only a solenoid click when the ignition was turned, two days later. A further starter was fitted and that "went" last week(after 4 months) now its replacement on Saturday has only started the car 3 times before going the way of the others.
Is it likely that this latest starter is in fact operational and the fault lies else where? I've read some threads on the original starting problem being linked to relay 109, can anyone give advice on this?
I've gone as far as locating the relay but would like some guidance before I go any further.

Thanks