ManUtd1999 has almost got it correct, although interest is only calculated during the first 24 months on the amount you have actually taken. My training started in August but I didn't take funds until December. The 2 year payment holiday started at this point and all interest accrued is only on the sum spent and not the overall loan.
The rate is also fixed at 3% per annum atop of the base rate set of the Bank of England, currently 0.25%. Thus, if the Bank of England increases rates as too does your interest and associated monthly repayments.
As a guide, on £70,000 my repayments in year 3-4 equate to ~£580 per month and then ~£780 a month until maturity at year 12.
In my case, I've currently only spent £51,300 and am accruing interest on this amount. Next month when I take another £5,300 out of the pot I will then be accruing interest on the £56,300.
Hope that makes sense.