Since I'm getting innundated with spambots on a CAPTCHA-free e-mail, this is my new form to try to safeguard against it. I'll leave this running a little longer, and if it doesn't give my any grief I'll put in on to my other sites. As far as I can tell this works, but use it at your own risk. I aim to reply to all message I get through web contact forms, so if you don't get a reply, your message probably hasn't got through.
Many thanks to these guys who kindly created the code for anyone to use.