I have checked the fluid and it seems ok.

There is no sign of any leakage under the car.

I can't select any gear with the engine on.

With the engine off everything seems ok.

I selected reverse with the engine off, kept the clutch pedal depressed and started the engine - when I released both the handbrake and footbrake the car moved backwards under its own steam (not gravity related btw) even with the clutch pedal as far to the floor as it will go.

It would appear to be in my laymans opinion something to do with the clutch not fully disengaging?

Your help is appreciated.