Hi all, just wanted to give everyone an update as I hate threads that never tell you what finally fixed the problem.
I fitted a new battery and that resolved the problem with the battery being flat after only a couple of days of not being used, then I got the fault codes read with a snap-on diagnostic reader and it showed these fault codes
P0404 egr control
P1613 engine stability controller
P3505 glow system
P3515 airco power output
I found that it does have a map sensor so I disconnected that and it ran much worse and wouldn’t accelerate at all when driven so I reconnected that and as the egr had already been cleaned and I didn’t know what the other codes meant I took it to a diesel specialist who said the injectors need to come out and be tested.
So that was done and all 6 injectors failed the test, so they were rebuilt and it now runs perfect. So it was bad injectors.