Update:
Finally got round to doing the job yesterday. Found that the biggest problem i had was getting the car on the axle stands. Couldn't get enough clearance from the jack i had so had to go on a mission to find a better one.
Once that issue was solved i got to work on draining the oil and getting the sump off. Used a ball end hex tool for the sump bolts, making things very easy and straightforward. Once the sump was off i instantly saw my problem. The pick up was in a right mess, covered in bits of dipstick and general oily crap. Replaced it, gave the sump a good clean with a drill and wire brush attachment and then put it all back together.
Only driven it a few miles (enough tho for the issue to be highlighted again), but so far so good, no warning lights, engine and turbo both sound fine. Touch wood, i think i've got lucky.
Cheers for the help. If anyone has a car with this engine, and it is upwards of 100k, i'd definitely recommend spending the money and doing this job. pretty cheap and easy to do and a hell of a lot better than paying for a new engine!