GrobblySquirrel,
having been through the system a few years ago, but I imagine its the same now. My salary is reduced by the amount of the bond being repaid to me. Example. My SFO salary is £45k, 9k less than a 'normal' SFO. That 9k is paid to be net of tax. You do save about 400 a month of tax, so its quite useful, but you do not get that 9k in addition to your salary.