OverWyreGrower, I took the lazy route, mainly as all my plums are very small (nothing larger than a ping pong ball).

I just poached mine in a heavy syrup (125g/4oz sugar to 300ml/½pint water) kept stones in and skin on. Some I then saved to eat cold (great with yogurt or ice cream) some when into a crumble. All in all very successful, especially as we didn't even know we had plum trees .