I just did some calculations based on my teaching experience - and some generosity with hours worked in evening / weekend / holiday time.
About 1900 hours* spent doing teaching work - class work, planning, marking, working over holidays etc. It could be less than that but I am not sure if I could make it more.
On £43,000, that is £21.57 an hour all in
On my current salary of £41,000, I get £21.75 IF you just look at my contracted hours worked during the year and the holiday hours. If you ignore those and just look at actual hours worked, then it's £25 an hour.
Supply teaching - 8.30 - 3.30 = 7 hours. Take away lunch and that's 6.5 hours.
In that time, an experienced teacher would have earnt £140 (6.5 x £21.57)
So a supply teacher who has far less responsibility is earning £119 (just 15% less) than a teacher with full class responsibilities.. Which is not too bad really.
*Actual hours worked in a year might vary between teacher