Right, have looked at this again tonight, it has broken off flush with the block face which makes life difficult, have ordered some easy outs so will see what I can do when they arrive-was going to add a photo on here but don't know how to do it!
Anyway, only problem is when I put a screwdriver into the hole it feels like there is no back to what's left of the t-Piece thread-it shoud be solid with a small hole in it. If something breaks off within the oil pressure gauge hole in the block where would it go-down into the sump? Not sure what the back of the oil pressure gauge gallery opens up into and cannot see right down it!
Thanks