I ordered BT Broadband with a Game Router a couple of years ago for a friend - he had ISDN, so ordering from anyone but BT involved ISDN cancellation charges, and going with BT got him a free router. It went in on time and has worked just fine ever since.
The BT Game Router, at least, works with Linux, its accessible in the usual way from a web browser. I was a bit surprised to discover that it came configured with the firewall off and no password or user name or configuration guide in the documentation. Maybe that is somewhat understandable in a Game Router. However, calling support got these quite easily.
The main reason for buying from a reseller rather than direct must be price. If you look at the pricing from Tiscali, say, as compared to BT Retail, there's around £100 a year in it and no difference in service. They really need to get the fat out of Retail.
We ourselves bought Tiscali, threw out the usb modem, bought a Hayes one port modem/router from Ebuyer, and hooked that up to our ethernet hub. I had to call Hayes support to get it configured right, but they were wonderfully helpful and very well informed. Tiscali, or the router, seems to lose the IP address every three or four months - which rebooting the router fixes. We are not very demanding users, but it works fine. My neighbour, who is a more demanding user, also has Tiscali, also provided his own router, and is quite satisfied.
Regards,
Peter