Fed up with the problems.

Even when the car is warm, it takes about 10 seconds or so + to turn over. It will stay trying to start at about 300rpm and ill have to keep the key turned for 10 - 15 seconds before it starts to turn over.

Fearing this is damaging the starter motor etc i need it sorted. Any ideas?

Maybe the temperature sensor? Quite cheap part if I remember if it is the case. Best bet is trying to get it scanned, see if any errors pop up.