Having just picked up a customer with a Vodafone Suresignal box, I can confirm they work well when they're working.
However, their setup process is somewhat temperamental, and they do have the ability to interfere with wifi if the box is too close to your router.
If you have one, i'd suggest resetting it and trying again.
(and upnp is less of an issue than you're making out, especially for a home situation)