There are, I think, various 525 JCB's, so make sure you are comparing like with like. An Ag. spec 630 or it's yellow equivalent will be just fine. The usual caveats of dealer support and condition of the used example apply.

Check for signs of abuse and care, tyre condition (they eat tyres on concrete) etc. I'd be inclined to give it a major service before you start, changing all of the fluids. They are the sort of machine that is first to start, last to stop, nobody looks after them, but the whole operation falls apart when they stop working.