Cold engine fault

[Galaxy quest]

Hi , I know nothing about cars so try not to get to technical please.

I have a 55plate 2006 ford Galaxy ghia 1.9tdi and when the engine is cold the car won't go above 15 mph. 

If I sit and warm it up for 5 mins or so it works great.

After some advice I changed the Maf sensor, map sensor and the air filter, but still does the same.

It starts first time everytime, no other problems apart from this.

I would be grateful for any help and advice.

Thanks