I knew this was going to happen, eventually.
Now TV have sent me a letter informing me I can exchange my Standard Definition (SD) decoder for a High Definition (HD) decoder box for free!
I only subscribe to one channel (MTV, which is SD)
Woohoo! (I haven't switched on my decoder for months, but free is free!)
If you're a Now TV customer with an SD decoder, perhaps you can call them and request an exchange too.