Finding entry level/trainee positions... finding a career

[NeverendingR]

I'm a 25 yr old girl from London who is in a bit of a funk at the moment career wise. The main issue being.. I don't have one.
I've worked on and off since leaving school in 2000, but it's been mostly in retail, which (If I'm being honest) I find pretty soul destroying and I absolutely hate it and can't imagine working in retail for the rest of my life.

I know I need a career, especially at 25, soon I'll be wanting to settle down and start a life for myself.
But I feel I'm so far behind all of my friends, most of whom have qualifications, degrees. NVQs or at least reasonable work experience. I on the other hand have nothing.

The other problem I'm experiencing is not knowing where to start.
It's clear I need an entry level position somewhere, get some decent on the job training and work my way up the career ladder but I do not know where to begin! I don't even know what field to look into. I'm just really hoping somebody out there can give me a few ideas, a few pointers, careers which generally let people in at entry level and that sort of thing.

Can anybody help?