I'll put a new glow plug controller in it and see if that resolves the glow plug fault codes, if not i'll give it a set of new glow plugs.

Re: the fuel rail pressure, Is there any procedure to isolate and test/replace just the flow regulator on the hpfp? I'm hesitant to start throwing major parts at it without being 100% sure (or as sure as one reasonably can be).