The garage could not get me the fault code but provided a print out from the diagnostics tool. The EGR valve was stuck, not blocked .. all cleaned and in working order now.
Apparently this can happen if the car is left sat for a while, which it hasn't, not since I had it anyway.
Also not a common issue that the guys had seen on this version of the engine.
Hopefully that's the last of it as I've had EGR issues on a car previously which eventually forced me to get rid of the car !