Just as a passing thought and before I troubled anyone, I have tried another contact form that I got off the web.
Rather than just replace the form with the new one, I rebuilt the page and checked the validation at each stage. Finally managing to validate it to XHTML 1.0
The original form was from 1 and 1 so it seems possible it could have been the form that was at fault. Or my page make-up was in such a mess the form would never have validated. Knowing me it's more than likely the latter. Either way it's validated now.
Perhaps one lesson I've learnt is rather than try to bash on and maybe make matters worse, is to start from scratch with a blank page and as you suggest validate as I go on.
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