Right, I am going to try and do a full description of where I am and what has been done to the car.
Since the above post, I continued to use the car, but the starting problem got worse, as it needed cranking from cold as well as hot-with the occasional time when (hot) it would start straight away...
It also cut out under hard acceleration a couple of times, which had never happened before.
So eventually I bit the bullet and decided to have the 4 injectors that hadn't been touched overhauled. This was done and had no effect on the starting, so I took it to S&S diesels to see what they could find.
They played around for ages, substituting sensors and testing the pump pressures, low pressure pump supply and anything else we could think of.
The conclusion was that low fuel pressure is causing the problem, but that the pump is more than capable of supplying the fuel at the correct pressure, but is being told not to by the ECU.
So....either the ECU has gone doolally and is getting more
doolally by the day..(likely?)...or something is telling the ECU to cut the fuel pressure (more likely?) but we can't find out what the hell it is.
And now after getting the car back from S&S, it drops in to limp mode under any kind of load, and cuts out under any kind of acceleration...see this other thread for the latest.