Yeah I called in recently and they said they only deal with recent bereavements!
I've identified and visited the grave and number that I'm wanting to find the plot owner of!
I assume it's a family member as the grave is my Grandad who passed in 1959 and there's been an addition of a plaque for my Uncle who passed in the 1993! I assume that my uncles family would have the deeds to be able to put on the plaque!