When setting off with a cold engine is OK until I accelerate moderately and the glow plug coil symbol illuminates and the engine goes into limp mode, this is on a 1.6Tdi VAG DBKA engine. If I then stop, turn ignition off and re-start engine the coil symbol is out and all is normal. To cut a long story short the problem is due to a faulty oil pressure sensor especially when the engine is cold.
There are two oil pressure sensors on the engine, 1 for low pressure and one for higher pressure.
The garage diagnosed both sensors were failing, they were replaced and all is back to normal.
The garage ( Non VAG) told me they are getting lots of VAG vehicles with this problem so now keep replacements for both sensors on the shelf.
So double check the oil level manually and if OK get the oil sensors diagnosed and replace but make sure they are OEM grade and not cheaper lool alikes.
The sensor with the grey plastic body is the high pressure and the one with the green plastic body is the low pressure sensor.
Hope this is useful to others with a similar problem!