The only time I've received free ones, is when I first subscribed to the 20Mbps package, then when I upgraded to 50Mbps, and then when the free 50 Mbps router was giving me trouble another free one was dispatched.
So in Total 3 routers for free but not in the same way you had hoped,
I wouldnt pay £50 for a router supplied by VM though as Ive had them all and don't rate them very highly
I,m no expert by any means so take my advice with a pinch