You need a serial number to get the code to unlock the radio. Hold the 1 and 6 button to get your serial number, it should start with an M or a V followed by 6 or 7 digits. If this isn't what is appearing on your screen then try button 2 and 6 instead. If this still doesn't work then you may have to take the radio out and read the serial number off of the radio label. Removing the radio is fairly simple, there's plenty of videos of how to take it out online. If you have a serial number starting with M, go to this website and enter the numerical part of your serial number (if you don't want to pay £1, you'll have to wait about 30mins to get the code): www.pumapeople.com/decode.php

If it starts with a V then this online unlocking service charges 99p: www.ebay.co.uk/itm/Ford-Radio-Unlock-Code-M-V-Seri...5

If the code is still wrong, i.e. the radio doesn't unlock, then don't keep entering it. The radio is designed to lock up if the wrong code is repeatedly put in, and that's not an easy fix. It's hard to say for sure without seeing the radio, but it sounds like your radio has had it's original code changed. After you try to get the code as I've advised, if it still doesn't unlock then I'd recommend ringing your local Ford dealer and asking if they can recode it for you, or if they can suggest someone who can.