This follow on from my last post. ( Thanks for those who pointed me in the direction of the BT firmware update while I was updating my previous post , you are keen!!!!)
I am always laughed in my family for my habit of reading the instructions and I always tolerate this with good humour because who do they come to for help when something doesn't work.... you guessed!! ME and with a smug smile I point them in the right direction. Sooooooo guess what I didn't fully do with my 10v?...... yep I didn't look all the way through the supplied manual, (I do prefer paper instructions though!!)
So after my last post I had a wander through the CD manual supplied with the 10v and found out about how to access it through a web browser as described in my previous post.
I discovered that there was a section in the router where you could check for updates and lo and behold an update was available, so after saving the current configuration I downloaded and installed the upgrade from within the 10v menu very easily.
At this point I didn't test the 10v cutting of off external calls on the BT landline as in browsing around on the web I found a hint that UDP and TCP can be used as the same thing

so I changed the port settings, as described in my previous post, in the Belkin router to TCP and things seemed ok as I was not locked out from the internet as before.
I have now found on a couple of test calls through the BT line using a mobile that I can answer the phone without getting cut off. This may be due to the firmware upgrade or something else entirely different.
If anybody has any further suggestions about these UDP settings I would be grateful