E430 gearbox

[k595]

Hello

Not a very thrilling one this I'm afraid - I've got an old E430 estate S reg 115,000 miles the gearbox is playing up changes down sometimes instead of up, clonks a bit anyone got any ideas does it need some new oil ? is that possible or is it simply on the wayout?

Any one know of any decent specialists for this sort of thing near Bath / Bristol / South Glos

All help much appreciated

Cheers