I may be wrong, but i believe BA still have some type of group interview - to see you work/interact with other people - during this they are mainly trying to weed out those that are A)overbearing , B) Don't participate at all !!
Then you may have a 1 to 1, or 1 to 2 interview which may last 20-30 minutes or so.....
I know for a fact that they are looking for people who will join the airline with a high level of commitment (regardless of fleet which everyone always wants to know) , and also who works well with people and if they've flown previously will not keep rattling on about former work experiences/positions and so on...... !
The maths questions are relatively simple, but you should be able to do multiple exchange rate conversions in your mind at a reasonably fast pace . . . . you may be on a quick flight where there is no duty free computer and you have to serve people pretty efficiently.
Relax though,most of the interviewers are crew and realise people are nervous!
Good Luck
