From an ex nurse..... DON'T
Plenty of other roles you could train for, Graphic design wont get you credits but pay would be better, hours would be better and you wouldn't end up broken like so many.
Consider things like occupational therapy, art therapy, even physiotherapy if you liked science at school. You will probably need to do an introduction to healthcare course whatever you choose. Local colleges do these and they often start at intervals during the year.
The alternative would be to work in a hospital as a health care assistant, go through the nvq route over about a year, getting hands on patient care experience and then apply for nurse training if you still want to. It's something you really shouldn't do unless you have a proper handle on the reality of it.