I currently charge £35 an hour which was the rate suggested by my professional association a few years back. I know that slightly nearer London, the rate is £40 and in London £50.
It's my sole income and I pay tax etc on it, buy materials and photocopy etc. Plus wear and tear on my home!
I am Herts- 35 miles north of London. I feel I am undercharging as most A level tutors charge £30 and I have much more specialist training ( used to teach A level soknow the difference).
If you are a paarent in the SE would you pay £40? ( assuming you could afford £35 anyway.)