Final update on my problem

I was told my oil cooler needed replacing, so I've had the old one pressure tested and it turns out there was nothing wrong with it, no leak nothing, and I've now sold it on to get some money back, the guys told me his car is running fine with it fitted and boosting great, ( he says he's happy as a pig in shi7) so that was a waist of time fitting a new one, also, the old fuel filter has been tested by a customer of mine who works for York university . He took the old filter and cut the bowl off the housing and did a fluid pressure test and confirmed that he couldn't raise enough pressure through the filter to keep a car running, he said it was so dirty you couldn't force air through it until he cleaned it, so I'm 110% sure this was my problem all along, and the garage I took it to didn't have a clue what they where doing and if they had fitted the fuel filter when I had asked them , we both would have been happy,

So if you get any problems guys like mine try the fuel filter first, for £35 it's got to be one of the cheapest options and sorted our problem out, I'm sure