I tried that link but got repeated error messages when I entered the serial number. However, I e-mailed the codes to contact@freeradiocodes.co.uk and they sent back 2 possible codes within an hour or two. The 1st one worked perfectly. Really good, friendly service - and actually free, unlike others I looked at. Great tip, thanks!
In the meantime I had tried freecarradiocodes.com - and stumped up £4.99 for their premium speedy response ....... and heard nothing for 15 hours. E-mailed them questioning their honesty/integrity and got a reply within an hour, including the same 2 codes as the free service, so fair play to them, they did deliver in the end.