Patio fruit trees

I must admit I have not heard of this variety, but it sounds like it is probably a type of Zwetsche (German) or Quetsche (French) plum, usually purple or blue in colour - popular in Europe but little known in the UK. I would be interested to hear how you get on with it. Does it say what rootstock it has been grafted on?

No it doesn't say which rootstock. It is just a typical patio tree rootstock which is very dwarfing It is probably about 60-80 cms tall and the garden centre said it just bushes out. I have a holly and olive tree with a similar rootstock. I will see what happens!
A friend says the plums are lovely and make a good alcoholic drink

i dont know is this link is of any use to you?
6ft+ Prunus Hauszwetsche, Prunus Domestica Hauszwetsche - Tree

If the rootstock is not stated, walk away and buy something else that does state the rootstock.

One person's dwarf is another person's medium-vigour.
Another person's dwarf is anything remotely smaller than a full-size tree.
Some people describe apple MM111 rootstock as "semi-dwarf" - yet it is capable of becoming a big tree. They call it "semi-dwarf" because it isn't quite as big as the wild type (about three-quarters maximum potential).

The vigour of the variety grafted to the rootstock can also make it get bigger than you'd expect.

Only a few months ago we had a "patio" cherry tree on Gisela (dwarf) rootstock which had reached 7ft in its second year and looked like it was good for another 3ft of growth for the next year. Turns out the variety grafted to the rootstock was a real monster which was overriding the dwarfing effect.

Certain varieties will override a dwarf rootstock. Bramley apples being a well-known example. I have a Bramley on M26 (semi-dwarf) rootstock and it grows as fast as some of my trees on M25 (full size ladder-required-trees). Suffice to say that my "semi-dwarf" Bramley is capable of becoming an average size apple tree because the Bramley bit is overriding the rootstock.