I really don't know how the UK works....but in the US, I would recommend obtaining an associates/bachelors degree in nursing first. this is because you typically need the degree to qualify for licensure as a registered nurse.

I have heard that there are now programs available over the internet in which you can obtain the classroom portion of your degree, and it is to be supplemented by clinicals in the field. An associates degree would be the quickest route because they are typically 2 year programs.