Thanks James, have already ordered the one that Martin mentioned and am still trying to download the app to my phone for realtime updates whilst driving.
DPF has been on for about 10k, majority of which is dual carriageway mileage and there has been no changes at any point prior to or since it was changed. Fluid is something I asked the garage about but they said that the dash will light up a warning when a fill up is required. Is that right do you know??????
We have been looking at the fuel pressure sensors as a possibility but it never shows any fault codes and my mechanic is feeling guilty at how much of his house I've paid for now.
Someone in another post has mentioned injectors being out of 'sync' and as fuel looks the most likely issue it's something I'm now looking at on here. We discussed checking the fuel pipes for blockages etc earlier today funnily enough.
Thanks for your input