was told by aa man who recovered me home that head gasket was gone (he did a sniff test which changed colour) was then told could be heater matrix(heater not working inside damp window wet on inside) .tried a matrix bypass starts fine no oil in water or water in oil but has a leak which comes out around gearbox after running for half hour or so (keeping water topped up) steam comes from back of engine (back right near battery) turned off and could hear bubbling and steam but could't see a thing.anything i can check or is head gasket gone?

Sounds like the water pipe that feeds the turbo has split its a right pain to change,your better off putting the car on some ramps and looking from underneath the car with an inspection light around the top off the bell housing.

If it,s a turbo it could be a leak on the turbo cooling pipe , one of mine sprung a leak , it didn,t leak when running , it was shortly after switching the engine off steam would start rising from near the battery .

Just bear in mind there are loads of little water pipes in , under and around the plenum which can spring leaks , the best way to stop those leaking is to do a plenum bypass and eliminate them alltogether . HTH