Does the starter turn it over quickly or does it sound sluggish? I thought mine was OK but it turns out that the starter was not churning over nearly quickly enough. Always seemed worse once the weather turned colder. A known issue in the diesels. Made it a bitch to start.

It's not really cold enough yet to need the glow plugs. These diesels start pretty well without even approaching freezing. I found the glow plug controller was broken on mine. I think I have a new one that will suit your pre-facelift E53 that i bought in error for my facelift.

Where in England are you?