There's a little law called the DATA PROTECTION ACT that makes it illegal for companies not to disclose any info they hold about you. They are at libertly to charge a fee for providing the info (i believe a max of £10, but don't take that as gospel), but it might prove a useful route for those (including myself) who want tho know where they went wrong.
I cant say whether you'd be better off trying NATS itself or the HR company? And if the info has already been binned then it might prove a dead end, but if the info is there they have to tell you!
more info at
http://www.ico.gov.uk/documentUpload...cess%20FAQ.pdf
Having said all of this i am no lawyer, and take no responsibility for the outcome!