Hi groov. you maybe didn't read my orginal post fully.
The phone I use works fine away from the office. IE, away from the sure signal I get a 3g service on my phone. I have 2 phones, one 3g tablet and one laptop with mobile broadband. All exhibit the same problem through the sure-signal attached to the 2850, yet they all work fine through the 3g network on the other side of town. I can make and receive phone calls and texts and get access to the internet via 3g. At home through the VSS attached to the 2850Vn, I can make and receive calls and texts, and even though the phones/tablets etc display the 3G/H symbol, they don't get internet access. Any app on the handsets just waits and waits then times out.
It's not the phone.

There's a very useful thread here....
http://forum.vodafone.co.uk/t5/Vodafone-Sure-Signal/BT-Infinity-and-Sure-Signal/td-p/1039993/page/3
....that discusses the problem and possible solutions. It only partially works for me.
I can at least make and receive calls and texts, and with w-fi turned on I get the internet access through my access point I need on those handsets, but having 3 radios turned enabled on the handset drains the battery pretty quick (cell, wi-fi, bluetooth).