Cesc, it will depend on the total amount/type of the loan involved. Something that's worth noting, and which has been pointed out a few pages earlier in this thread (posts #1235 and #1237), is that (with the current deal) when payments begin (after the 24 month holiday) they are set at a lower rate for a further 24 months (something like 75% of what the remaining payments will be). Even with the largest possible (BA guaranteed) loan it is covered (give or take a tenner) by the £1000 payments.
This means a number of things. For those taking smaller loans, the £1000 BA are paying on top of their salary could create a surplus for those two years. You could choose to pay extra (even just up to the £1000) per month, hence slightly lowering your payments for the remaining years, or just budget for the slightly better 'salary' created during that period. By the time the payments (with interest) increase (potentially to over £1000 per month for those having taken loans of sufficient size), you would be at a higher point on the FPP pay scale. Even those taking the largest loans will not feel any real impact on their actual salary whilst they are at the lowest points on the pay scale.
Even when having taken the largest loan with the higher rate of interest (i.e. not property secured) it looks very manageable.
Some people may be in a position to make higher payments earlier on, leaving them more comfortable with the later payments and paying back less interest in the long run, others may budget to keep the higher payments until after the initial window. There's a framework, but it's not rigid.
Anyone getting to the final stage will obviously have an opportunity to chat about salaries and bond repayments in more detail with the recruitment team, which will be far more accurate and enlightening than anyone can or will post on here. BA cannot, however, provide anyone with financial advice, they can only make you aware of the possibility of a loan which may be guaranteed by BA. Neither BA nor anyone else can quote you specific numbers about repayments as this will be entirely between you and your finance provider, which in most cases will be BBVA. All BA can or will ask is that you have considered the financial routes and implications involved in taking up a place on the scheme, then effectively pass you BBVA's business card if you want it.