Hello David, on the disco so I'd say it was sh*te.
There is always a fair bit of play in the front prop, not many disco don't have it, a diff can be picked up for £30-£50 and changing it involves undoing 4 bolts on the propshaft where it meets the diff, draining the diff, removind the half shafts in the axels, held in by 5 (I think) bolts in the centre of each wheel, and undoing the bolts that hold the diff to the axle.
Take it out, put new one in with new gasket or liquid gasket, put half shafts back in with nes gaskets, fill with oil, connect prop and away you go.
Total cost less than £100.
I'd try the 4x4 specialist mate.