Problem was hosting
Fasthosts proved totally inept, not really looking into this problem and just pointing the finger at the script.
Eventually said they did not support email re-laying, althi=ough it did work in some domains on their servers, figure that
I CAN CATEGORICALLY SAY ISSUE WAS FASTHOST NOT WEBASSIST.
Moved to 'Clook' (www.clook.co.uk) for hosting, very very helpful people highly recommended. Hugely configurable hosting.
All now seems to be working ok.
thank you WebAssist.