Oh dear, just had the dash bing at me and flash up "Engine Fault Workshop!" along with the glow plug symbol.
Luckily I was only a minute away from home so I just cruised and didn't actually notice if it was in limp mode as I took it slowly anyway.
A quick search seems to point towards some sort of sensor or wiring issue and though I have an old VAGCOM cable, it's a cheap blue one off ebay so I doubt it'll work with the MkV to find fault codes.
Thankfully the car will be going back into VW soon for
some warranty repairs but this will mean a 20 mile drive to get there, I hope it will be ok to do this?