if they are not an authorised monaro dealer (even though they sold it they may not actually be an approved dealer) they will not be permitted to do any warranty work.
From memory the south west dealerships are bristol (avoid) or Picador's southampton
ok then that bad will see where yeovil intend to send it for repair if they say bristol might take it to southamton pay out of me own pocket cant see it being a big job
why take it to yeovil? They are not even authorised to look at the car, as pathetic as it sounds it requires an authorised dealer to look at it and book it in.
When you have your rear tires changed, dont let the fitter stick a stand under the diff and lower the ramps to lift the back end. It'll make the diff leak again.