Cancel and re-subscribe? Not sure if we did this, but somehow we got a new box and dish installed for whatever the new customer rate was at the time - although this may have been when we changed from sky to sky+, but still got a new dish. Worth a google though.
Or alternatively, run an extra Sky feed from the dish (should be a spare feed available if you have one to the bedroom and 2 to current sky+ as they would use a LNB for four feeds) or re-route one of the sky feeds from where your sky+ box is atm. But you would need to get a new sky+ box. Not sure how much sky would charge for this but you could probably get one cheap from ebay or other sites.