Bit more reading reveals this:
"... diesel specific oil is higher in detergents. These are needed in modern diesels for lots of reasons. Diesels rev much lower than your petrol engine. Therefore a diesel specific oil, as opposed to a non specific oil (oil suitable for petrol or diesel engines) but still meeting the same specs, does have a tendency to foam more in a higher revving petrol engine. I found this out during our testing of a new engine last year during which we bench ran several engines to destruction on different oils. The diesel specific oil in petrol engines gave the least amount of protection at high revs due to the introduction of air into the oil galleries caused by foaming."
So Ill use the TD oil Iv bought im my mums MK4 TDI PD 130 and buy 5w40 petrol specific for mine.
Thanks for keeping me doubting and searching for a solid answer guys.. You may have just saved my engine