Thanks for the information Greg. I thought with this being an issue from it's early days that has got worse that it was unlikely to be the glow plugs but I'm happy to take the advice of someone who knows better :)
I used to have a local mechanic that I could trust (friend of the family) but I've moved and lost that contact and to be honest the confidence - and I'm relying on main dealerships where the labour costs are high, I've heard stories of "trial and error" repairs sometimes and I can't afford to throw that kind of money around.
I'm booked in to ***** ***** main dealership for a full diagnostic check on Thursday morning, dropping it off on Wednesday night so they get it as a cold starter on Thursday.
Thanks for your help