+1 Norm.
Indeed, when I started the scheem I saw £70pm NET deductions on my salary slip, and had an angry moment before comparing take home to the previous month, to see that once other deductions had been factored in, the gross was far closer to £50.
The 25% is also an absolute extreme and Fair Market Value has always been part of the final payment in the scheme, so shouldn't have been a surprise tbh. There are a number of 'official' ways to get that down, such as extending the contract (but not the payments) so that another year or two's devaluation is taken into account.
The savings are far greater than your calculations show, jdrussell.