As long as you're not expecting them to be round, firm and fully-packed when thawed, they freeze just fine. I'd recommend de-stoning them first, since, as has been our experience here in the U.S., they tend to have an 'off' flavor if not pitted first. Some have likened the flavor to an almond overtone.
Don't peel them, just halve or quarter to remove the pits. We do the freezing two ways. First, if time is of the essence, simply place them in a container and freeze. Otherwise, I like to place them on a cookie sheet, and put them in the freezer for a day or so and then remove and place the plums in vacuum bags to seal. I've said it before, if you plan on storing much food in the freezer a vacuum sealer is a terrific investment, costing about $100 or so here.
The purpose in freezing them first and then sealing is that the vaccum bagger heat seals the end of the bag when the cycle is complete. Often, the plums ( and other such fruits and vegetables) leak some of the their juice, which is then drawn out by the vacuum process and doesn't provide a good seal...
Our vaccum sealer also provides special hard plastic container that are vacuumed out of the top with a tube attachment. In that case, I freeze whole, pitted plums...
Best of luck!