Hi everyone thinks head gasket, the usual culprit is the oil cooler a rather snazzy little device that normally sits below the oil filter housing, it is a box that allows water and oil to circulate around each other through different channels so the oil cools, problem is the gasket fails and allows the two to mix, fairly cheap fix just a bit fiddly and requires a coolant flush after to get rid of the oil in the system, Vauxhalls are notorious for it, done a few of them, gearbox fault will require a diagnostic scan to reveal what's going on.
Steve.