Re-reading your post, Richard, this was the bit that tripped me up:
Originally Posted by rdenning
It was good enough indeed to be sent for by a publisher who although rejecting me did send a 3 page letter discussing its merits and areas of improvement and asking me to send more material.
If you got this level of interest from a publisher and were asked for more, why didn't you follow up? Did they reject a second submission, or have you not tried yet? It looks like a great opportunity missed!
Oh, and when you say "sent for", did they request sample chapters and reject those, or was it the full manuscript? Sorry if I sound nosy, but the submissions process is much on my mind at present...