The CAA dictate that a 170a is required. For CPL the person signing the 170a does not need to have flown with you but they must for IR. I think it is designed to prevent you wasting the £729 test fee (plus aircraft hire) if you are not up to standard. For the poster that has failed the 170a three times so far that 170a signatory (by not signing it) has saved you over £2000 in test fees alone!!!
Maybe you didn't think of it that way
You will all end up paying for the highly experienced instructional staff somehow, either directly or through higher hourly rates etc.
PS EK4457 see page 10 of the brochure............it's there, it dosen't mention cash though to be fair