Runrig fan, it implies it is a separate work.. The Vatersay Boys had nothing whatsoever to do with it. The lyrics (and tune) were written by Hylo Brown and already posted.   They Vatersay Boys credited Hylo Brown. It is not the artist performing a modern song or tune who should be named, it doesn't make it a variant - it's just another recording of the same copyright work.

This is the recording ID on the MCPS/PRS database. EMI own the publishing rights to the song.   

        I've Waited As Long As I Can
VATERSAY BOYS
(Brown)        
Shibhalba Ltd        EMI MUSIC PUBLISHING LTD.

Anyway, enough said! I'm not sure why this thread was revived when everything was covered. Hylo Brown wrote I've Waited As Long As I Can, around 1959. He and his band first recorded it about 1960 as a single. It's a bluegrass song revived in Ireland and Scotland in a Celtic/Country crossover fusion, sometimes under a false title 'Say You Love Me', and sometimes with a spurious Trad. claim. Many properly credit it, some chance their arm.