i wentout in my car last night and setting of from a junction it reved quite high and set off slow
further down the road it reved high again then i pulled into a farm gate to turn round and when i put it in reverse it went forward
now it seems as though it is stuck in drive
we have had it on diagnostics today and nothing has been found
i have been reading comments all day but dont know what the best thing to do is
can anyone come up with any idea's please

 

Normally pretty good boxes, so long as you don't overheat them.
They of course do have their problems though, first thing to do when losing drive, is check the fluid level, but I think this is pointless in your case.
It sounds VERY much like your forward clutch drum has gone, with the constant movement the circlip that holds it wears a groove in the drum.
They also suffer from overpressure problems, very commonly, but there is a modified valve chest and torque convertor that cures this.
The biggy is the cost, you are looking around £800 - £1000 for complete strip and rebuild to modded spec.
tabetha