One last thing you could check is if there is a director of a company with this name, bit of a long shot but might get you somewhere.
I agree that your best chance is Telivo, however, some registrars renew domains automatically and never charge the owners. I could show you quite a number of domains that are like this
So Telivo might not even have up-to-date info. Give Nominet a call and ask them if the domain is set to auto renew they should give this info out if you tell them why
Good luck