As I mentioned in my original post - the vpn does work through other routers but I cannot check this at my home location as the thomson router is the only one I have at home that is compatible with the plusnet broadband supply.
Re: the plusnet firewall - I must admit I had forgotton about this myself but have checked and it is turned off.
I have checked the required ports several times for this issue (bearing in mind I setup VPN's to external client sites as part of my job on a weekly basis, I like to think I know how to setup VPN tunneling).
Re DMZ's They are very complex to setup at the best of times and I really do not want to try this on the Thomson.
I assume this usergroup is moderated by plusnet administrators - I would appreciate some input from them.
Please please help me.