Citroen Dispatch struggles to start?

I have a 51 reg 1.9TDI Dispatch. Recently it has started to struggle when starting which is getting progressively worse. This morning it took 15 seconds before starting and in the last day or 2 the coolant light has flashed on briefly. I have checked the coolant and the level is fine.

Any ideas what may be wrong, don't want to pay a fortune for someone to find out when you guys seem to know your stuff

Thanks