@stewmath
Your tax calculations are pretty wrong. If the £1000 loan deduction is made before tax, that leaves taxable pay of £1,500 (based on your estimated £30k salary). Taking into account your personal allowance (2012/13 - £8,105), then you would actually be left with approx £1,200 each month. Much more positive result!
But, as FANS says, don't get too hung up over the numbers. So much of the details floating around on here are rumours - wait until BA announce the details. And if you can't afford the BA scheme, you'll only be able to make it in this industry by getting onto to a fully sponsored scheme such as Cathay.