Jusy wanted to mention that my regular Computer magazine "Computeractive" has suggested that unless you require to use Port Forwarding on your router for games etc then it is advisible to turn both off on the Bt HomeHub.
Apparently rarely used, this protocol lets programs and devices bypass a routers security without you manually creating firewall rules. These days UPnP is more likely to be exploited by maleware to attack your home network or use your router as part of a botnet. So, although this is a personal option if you do not use UPnP, it is recommended by the experts to switch off.
Please note, I am only passing this information on within the forum. To switch off on a BT HomeHub go to advanced settings, firewall, UPnP and turn both off.