You want Colletias, alias Barbed Wire plants. Go to http://www.hardyexotics.co.uk/ and check out Colletia hystrix and the even more extraordinary Colletia paradoxa. Now you see you really, really want them, don't you. (My wife won't let me...) We visited a garden in Somerset where they had both of them - they become quite large bushes. They get completely covered in flowers with a lovely scent to, hope that isn't too pansy for you. They are plenty hardy enough for Merseyside.