Thanks Boydie, I may post it next week and risk the embarrassment! It's happened to George harrison, Oasis, Jagger/Richards so I'll be in good company...
I have borrowed chords before when I was stuck for a chorus, which is fine as I knew I had to avoid the original melody, and there are things you can change ie different tempo, shorter bar length, different voicings etc to create a different feel. Plus of course, unless the chords are highly unusual they are unlikely to be truly original in the first place.
Whether this song is original or not, it highlights that the workings of the subconcious mind is intriguing to say the least.