Thanks for all your input girls

... Not quite sure how it got off topic with a sarcastic comment about how I'll be paying taxes (as if I'm not!) There was nowhere in my post that asked for advice on taxes but thank you for your irrelevant input

I thought it was assumed we should all be paying taxes, I shouldn't need to state whether I am or not.
Back to what I originally asked advice on, it's pleasing to find you've all had positive experiences making that jump! I'll definitely take the advice of making sure I have some savings behind me first. I currently have ZILCH. Totally sensible, of which I sometimes am not!

I've had a few hugely STRESSFUL days at work recently and in situations like that I just feel like giving up with no real thought into what the circumstances will be, I just want to RUN. After some thought, I'm going to grin and bear the full time job alongside building those savings up! I'll aim for 1-3 clients a week and I may even look for a part-time job if I get busier client-wise. Building it up slowly seems the sensible thing to do.
Regarding the couple of you that mentioned gaining some skills too, this did cross my mind and is something I could consider if I did venture into becoming self-employed. Apart from GCSE's I don't have any other qualifications and I'd definitely have the time to fit a course in around managing clients if I did decided to quit the full time job.
A part-time job is a great idea too, my family wouldn't need to know the hours I worked... Definitely something I could try!
Thank you so much everyone it's all been really helpful

(more is welcome of course!)