Fully agree with wearing a suit. At BA we see far to many candidates coming as if they are out for a night on the lash. As said smart business suit with hair contained, worth investing in a suit anyway. Get your mum to go out with you as she should have a conservative view. Hand bag is important too, make sure it is neat and not brim full to the top like wise practical shoes. You probably know this but also research the airline, its grouping, routes and future plans. So many people turn up with little or no knowledge of some of the hard facts, products turnover etc. Good Luck