Finding out where absent neighbour now lives

[martinnitram]

We need to contact the householder next door to a property were renovating, its been empty a while and nobody knows where the lady has moved to.
Apparently her husband died and she moved out shortly after that.
I've tried the council tax office as they know where she is, when you owe them money they find you wherever you are, but are hiding behind the data protection act, the electoral role tells me where she used to live, ie house next to the job which I already know.

Any suggestions where else to try
Thanks

[martinnitram]

I think ill put a letter in post, although postman is still delivering there so don't think there is a redirect on the mail.
No luck either on social media.
Thanks for replies.