So that garage did all the work on the car (aux belt, rear springs and the things they fit into, service, CV gators).
They said that the "whirring" from the rear was most likely the rear diff. It's been slowly leaking oil since I bought the car 8 years ago! Anyway, they had a good look at it and filled it back up with oil, but say that the seals (3 of them?) are gone and that the leak is bad enough to warrant replacing the diff.
They said that you can get recon units etc. They didnt seem to think the diff could be "fixed". Does the above sound right? Any ideas where I can get a new diff? How much should I expect to pay?