We've had the same problem and spent a couple of visits to Milleniun last time to try and sort it. Upshot is they can only supply a basic remote that will change channels. Not much use if you need full menu to retune etc. If you have a neighbour who has a working one they do work with any box but I appreciate its not a long term solution
We decided to bit the bullet and get a brand new box. Bit of a sledgehammer to crack a nut but we lost the will to live trying to sort it out