OK, Saint Ric has managed to get my lost emails back and present within Thunderbird but I'm still having issues sending email. It seems that I have a problem with my SMTP Server Name and possibly my username and password.

I would talk to Bulldog but their customer services/technical support shut at 8pm so I'm having to wait until tomorrow (they open at 8AM so I may try and sort it out before work tomorrow).

Many thanks to Saint Ric though for travelling all the way up to the wilds of North London to help me out. He had a hell of a journey too as his tube broke down and had to be shuntered to East Finchley!

Anyway, I feel a light is in sight. Hopefully this will be sorted in the next 48 hours.