So yesterday a new power steering pump mysteriously turned up and they fitted the whole new rear end. Service manager said car was all done and tested and ready to go. Thought I'd go for a drive with the manager before I left to make sure it was all good, and of course the new diff is really noisy, especially when decelerating from 110-80 and then from 60-40. Workshop foreman came for a drive and he agreed that it wasn't right and wasn't sure what problem was as the diff came brand new from Dana. So now waiting to see what will happen next