You should not have channels in the 800's, if you do you will have series and accurate recording problems since you are receiving from multiple transmitters. First of all you need to ascertain which transmitter your aerial is aligned on (what direction from Chelmsford does it point). Enter your postcode and house number here and tick I am in the trade Digital UK - Postcode checker This will tell you which transmitter you can get. Then you will need to delete all your existing Radio and TV channels and manually tune the correct mux. If you post the transmitter you will get nore detailed instructions.