Well, it's definitely not jumping out of gear and it shifts gears fine. It just rattles/clatters a bit. As soon as you dip the clutch the noise stops so I figured that either the bearings are going in the gearbox or something more terminal ahead.
I've dropped the car back to the garage now for them to sort it out. In my mind I know how it used to run and how it should perform. Currently it drives like the world's slowest thing on 4 wheels with your 90 year old grandma behind the wheel. Put it this way... even the baked-bean tin of a car (1994 Fiat Cinquecento 899cc) that we bought as an essential runaround until we get the Clio fixed... even this can out-drag the Clio up the slip road to the motorway at the moment
Hopefully, the garage will work out the problem and we can start to drive about in comfort!
In the meantime, if anybody has anymore thoughts on the problem then give me a shout.