Hugh, I have found the attached info on line so I know that it was in Eglwysbach. and a property search on rightmove showed these details:-
Llwynonn, Ffordd Gyffylog, Eglwysbach, Colwyn Bay, Conwy LL28 5TU
£180,000 Detached, Freehold 25 Apr 2007
It's a long single track lane but I couldn't see where exactly Llwyn Onn is.