This is really very embarrassing, but I thought since so many people posted to help me I owed it to them to post back with the result (also that and I'll probably never see any of you apart from on here

)
It was so simple, my ISP was blocking the inbound ports...I know that was one of the first suggested things to check, but since I have another site with the same ISP and
exactly the same plan, I assumed they wouldn't be blocking the ports because they aren't at the other site...it turns out because I am a longer standing customer they included the port blocking 'feature' along with free AV etc...
Once again thanks to everyone who helped, and my apologies for wasting time such a noob mistake
