What oil are you currently using? I ask because you state 'hopefully find some diesel oil'. Makes me think you are using regular oil. First use diesel rated oil, then try to find lighter weight (probably synthetic like Rotella or Mobil 1). I buy mine at the local farm supply store. It is called Fleet Farm here but there are many different versions. I'm sure most have diesel oil.
Of course you should check your glowplugs, but many have stated on here that the switch to lightweight synthetic adds 15-20F degrees lower of cold starting. I've always run syn so I have nothing to compare it to but I have done a -4F cold start this winter.
Here is the check list for cold starting problems-
1-Glow Plugs
2-Valves
3-Synthetic Oil
4-Battery/Alternator
5-Starter
6-Fuel
7-Engine (Compression)
It seems you can cross 4 and 6 of your list as you have a new battery, alternator and use Power Service (I don't and have never had a gelling problem even at -22F a few weeks ago).
Since I've owned my car, I've had problems with 1,2,4, and 5.
Each gave me problems starting in the cold.