I freeze my damsons (uncooked and whole) and when I am ready to use them just defrost and cook as usual. I spread them out on an oven tin and freeze so that each damson is frozen individually, then bag them, so that when I need them I can just take out what I need. It works just as well for plums.

We de stone them, then stew them and freeze when cool. They are then used in any Plum recipe and Yoghurt.
I believe they can be roasted too, then frozen.

Or for those inclined......washed, dried and forced into a big jar, sugar added then a spirit.....I have only done this with sour plums like czar or damsons.....then we use gin,
You turn and shake the jar daily until the sugar has dissolved. Keep in a cool dark place until christmas when you strain the fruit and drink the liqueur......and if you wish eat the"ginned"(or whatevered) fruit!

Or plum chutney

Or a table at your gate with bags of plums and an honesty box

I have a young Oolong golden gage not yet fruiting.....
You may be right about the yellow plum, a Leicestershire village has a Syston White Plum

Interesting you say that about the plums. My brother's in Gloucester, and he was told the yellow plums he has were an old local variety! I bet they're old local varieties everywhere you go, which would imply, a 'UK National'. I don't think they make a particularly good jam, and I've tried, with little success, as has my sister-in-law. Too runny, too sweet, and not as flavoursome as a good dark plum or a damson (my favourite). Hope that doesn't offend anyone who's just made a prize jam from the yellow plums!

One day hopefully my young tree will give us some........

Thank you all for replying. It's been most interesting reading your replies.

It doesn't seem to make good jam as I tried to do so a couple of years ago, there was no fruit at all last year, this year the trees (all kinds of fruiting trees) are almost at the breaking point for their branches, so loaded with fruit are they!

Jaykaty, you've answered one of the questions I was most concerned about - if they could be frozen without some preparation. So thank you again! :-))

I've stewed those I had brought home & putt hem in the fridge for the time being till I decide what to do with them.

Greengages are a yellow/green plum and I think they make a really nice jam. Certainly it is the one I like most on the hot crust from a freshly made loaf.