Dear Simon Cobb,
Maybe I can help you. I have a Grundig ST63 750 text and you have the same television. What you can do is to go to this link:
http://www.n-tronics.nl/ and you find there immitation remote controles. Than you need to have FB720 (the original is TP720A) remote controle or you can bye a Universal Remote Control and set the number what is nessecary for each television and the numbers are 018 or 020. Nothing else. So I hope that you are helped with that. Than on all the other way you can look on google or Yahoo searchmachine.
I hope that I have given you the best advise as possible.
Regards,
Jan Prins
Rotterdam The Netherlands.