Grand Espace starting/running problem

Hi, I have a 2007 diesel 2.0dci Grand Espace that has developed a peculiar fault over the last few months. It started that on the very odd occasion it would not not start first go and displayed 'check injectors' but would then start OK after a few minutes. This then developed into an issue when driving that after starting it would cut out unless revs were kept very high, also it would seem to 'miss-fire' when driving and needed to be kept in a higher gear as on two separate occasions it cut out completely. I took it to a local garage who only detected minor faults that had cleared themselves. He suggested changing fuel to BP (I was using TESCO) and this did seem to improve the running, i.e. no more 'miss-fires' or cutting out. I am still using BP however, recently the problem of cutting out after starting has come back but it seemed to happen more likely when parked on an incline, with the front end up, for a period of time. I have not heard of this before and wonder is it fuel starvation caused by an ineffective pump? Any help on this is much appreciated.