£200 a day seems like a lot. That is about £90 on top of my own wage. I am on long term cover (a term) and am getting about £110 a day for this. This is the same as I get for a regular day without the level of work. However I view the extra job security of a long term place as balancing out the workload, especially as half my classes are on revision and/or Btech. But I have had agencies that only paid £90 a day (£70ish after holiday and tax deduction) It varies by location as the pay gap was consistent in the 2 locations I would teach in. However in Bristol the only agency that ever got me work was the one which I knew charged the schools some £20-30 less than others as they had lower admin costs. I think as well most schools don't want to hire supply when they can "fudge" it with TAs, cover supervisors and internal cover, especially at those costs.