Some good advice here. This was my first year applying as well, so I am very pleased that I have been invited to selection.
My advice would be to do some networking - see if there are some people who can help you out with your application. If they fly for BA then that's obviously a major bonus. Another thing - do your research! Everyone says it over and over, but it really could make the difference! Read over the job description, and make sure you have addressed each requirement, i.e what to include in the cover letter. If you really are passionate about this career then it should be fairly easy to put into words, that said you may spend a lot of time moving things around and changing words trying to make it perfect. The thing to remember is that it isn't going to be perfect.
Of course, this is only my advice on improving chances of being selected for assessment, but there's more to the process than that - it's only the first hurdle of many!
As others have mentioned, I can only feel that some people have the wrong attitude here if the FPP is seen as the only way to the RHS.