Paul,
Not that I know a lot.. or even anything for that matter on the intracies of copyright laws of songs.. but I feel impelled to say this to you... let the company concerned take this "one" song from you .. obviously without any strings attached as to further recordings. Unless you think you can get a better deal elsewhere, you are faced with the enviable situation of having one of your songs made "public".. I for one am extremely jealous of you..

If as you say, this is the "first time", then I guess you have to take a risk or two.. just don't sell your soul to the devil...

I wish you well and hope you amass a great fortune due to your song writing skills in the future
Mick