39 pounds per hour seems about right to make a reasonable living.
When I think about my daughter, who is a 37-year-old psychiatric staff nurse about to move into a new job in intensive care which in this case doesn't mean inert people in bed with a drip but (specifically) men who are too violent to managed on an ordinary psychiatric ward, and already in her current work in acute admissions in London - she puts her life on the line every day in her job - she doesn't earn as much as I do (£26 per hour) for working one-to-one with people who want to do it and are mainly pleasant to me. I'm embarrassed to talk to her about money.
All those other payments you mention, with the possible exception of lawyers, you're not counting the amount which goes for overheads. I'm sure my hairdresser, whatever I pay to his salon, doesn't earn anything like £39 per hour! And I only go every couple of months, no way would I pay what I do if it was every week. Similarly with the chiropodist and the dentist.
I suspect you'll find that among the teachers on this forum, £39 is on the very expensive side of the mainstream, for weekly lessons. I could be wrong. Possibly it's mostly those of us who are on the "cheap" side who have owned up to what they charge. Yes, there's an ISM minimum recommended rate, but many of us charge less than that. Often when IU've taken on a new pupil I've been told that my fees are more or less what their previous teachewr was charging.