Chaenomeles ....common name Japanese quince.
Flowers can be white red, pink or orange...depending which one you find.
It might be Chaenomeles speciosa nivalis?
https://www.google.com/search?...
Chaenomeles x superba Jet trail is another white one that is sold in UK...but cannot be sure that is the one in your pic
https://www.rhs.org.uk/plants/...
