Grinding Gears!

I driver a 2000 TD5. Recently the gears have started to play up. Occassionaly (not all the time) when i try and put her into first or reverse there is a loud grinding noise. I also have this same problem when changing down in the gears. Changing up is fine but but going from 4th to 3rd can sound really painful.

A friend of mine suggested that it might be the clutch plates and if so it would not be to costly to fix.

Does anybody have any ideas?
Cheers

Barry

sounds like a clutch fault, either master or slave cylinder