Where abouts are you located in the UK, as I know of a couple of retired Lister Petter service engineers that are very familiar with the LPA/LPW range of engines, and may be able to help you out.
In a prevoius job I worked with Benford Equipment, and as I was leaving the LPA2 equipped Benford dumpers were just been introduced, never had much to do with them, other than routine servicing, at the time they seemed like very good cold starting engine.
From the compression pressure figures that you have quoted, that should be more than enough to get a easy cold start.
Another factor to consider is the spill timing (quite easy on these engines as you loosen the fuel pump and add or remove shims as required, under the base of the pump, this can be done without removing the pump)
Also poor condition of the fuel injection equipment will have the effects you describe, have you observed the spray pattern of the injectors out of the engine, ie turn the engine over with the injectors out of the engine but still connected to the engine fuel pumps.
It is an unfortunate aspect of the fuel pump design on these engines that they cannot be reconditioned, because the fuel pump body forms the element of the pump, so you will require a complete new pump if it has wear on the plunger or the bore which it runs in.