1.6 tdi cxxb engine starting woes

Hi all
My 2015 sv 1.6 tdi with cxxb engine has a starting issue getting progressively worse.
Freezing cold it starts immediately. Warmer conditions, warm engine etc it struggles to fire and stumbles into life.
Car has done only 20,000 miles but with many short runs and many starts.

I have considered replacing glow plugs and/or glow plug relay or even a temperature sensor (if knew its location).

No fault codes showing on vcds and no.engine lights on......yet!

Replacing parts just for the hell of it isn't an economical option so I am rather hoping someone can point me in the right direction.. to start isolating the fault before shelling out for parts. However, I will happily purchase parts if need be.
Has anyone else had this problem with this model and engine?
I see old posts for various types of diesels with similar symptoms so I'm hoping by now a fixing procedure might available.
Any help will be much appreciated.

Kind regards