I haven't seen the same product over here, but when I saw the plums coming along in the orchard I remembered it and thought I'd aim for something similar if the crop was a good one. The variety we're growing is 'Stanley'.
Mike and I harvested the plums today, fighting the wasps for them. There were over eight pounds in all - not bad for our first harvest - and I've converted all of them into preserve, in two batches. Once they'd been stoned and quartered, each batch weighed about four pounds, to which I added four cups of sugar and a little water. Then I just brought the mixture to a boil until my cooking thermometer read just under 100°C/210°F. As it's not a jam, you don't need to worry about reaching setting point and they don't need long cooking - about 15 minutes at boiling point is plenty.