Not being a Betfair bettor I'm not aware of any turnover tax.

Are you saying 1.2% of my bet is automatically deducted together with 6.35% of any profit? If I bet on 90% of the field I automatically lose 1.2% of each bet? If I bet on less than 50 markets/races/horses a week then the tax does not apply?

Sounds a like the dreaded Ned Kellyesque TAB where approximately 16% of the bet is gouged.