Airforceone...
The interview is not to hard at all...the main thing that they want to hear is that your company minded/flexible, and that you want to work for BA.
They will want to know what you've learned about BA in the last week, so get on the net and have a look at BA's website.
Also a big tip is when ever they ask you for an example of excellent service etc..they will want to know who benefited from your actions....you must stress that BA will benefit by getting repeat business, you must always say that BA will benefit first and foremost.
Another question they're very hot on at the moment is "which culture is totally alien to you"...you must say that you are very open minded and are always keen to learn about other cultures etc....you must also let them know that you can always find a way of communicating with people.
Apart from that all that I can suggest is that you make sure that you have an example for everything, if you don't they won't give you any points for that question, and they decide on your application by adding up your total.
Good luck......