Word from the mechanic is both good and bad. The oil pressure issue is just a stuck relief valve. Quick fix, low cost, easy peasy. Phew. The car will soon be showing 30psi on start up and 45psi on heavy load.

The bad news is the speedo. Gunge in the sensor right? Wrong. The diff is moving around all over the place and shifting away from the sensor. And on closer inspection there is a bloody awful racket coming out of it as well. The mechanic is going to take it apart and have a root around but if it's crown and pinion problems, or worn seals, it's going to need a rebuild. Bugger.

I'm too depressed to write any more. I'll follow up when the final news comes through.