Recently my turbo has been cutting out mid drive, pulling over and restarting would fix this. But now I don't think the turbo is working much at all I've changed the fuel filter oil filter and oil my next thought is the egr valve needs cleaning failing that n75 if anyone has any advice please help me I'm a novice at this and obviously don't want to have to get a new motor as when it was running well it was a lovely motor. Thanks in advance.

Common problem on diesels which many of us have had. It is caused by the variable vanes in the turbo not moving freely so trips into limp home mode to protect against over boost. As you have found it it reset by turning the engine off then restarting.

Search on here for stuck vanes, Mr Muscle, overboost, turbo etc. There are many threads to bring you up to speed.

Basicly the turbo vanes get gummed up by carbon deposits by being driven at low revs (like a granny) and made worse by an engine that does not properly warm up or take long runs.

Fix is by mechanical or chemical cleaning.

Sticky Turbo vanes for sure. I would expect that you'll have an overboost code logged in the ECU.