Solved it, as I assumed it was down to some problem with paths. As this was very new webspace my domain had not registered entirely with its new nameservers and because when I re-configured joomla and phpbb to use the IP *AND* the domain (temporary necessity to see my site work) the paths were messing up the operation of the PHPBB plugin connector. Now that my old domain is fully functional I have removed the IP prefix in the joomla and phpbb config and it all works!
Thank you to anyone who took time to read my post... but all is good now. No doubt I will be returning if I have further questions!
Regards,
Glyn