Thanks to a report from 5erenaur I paid a visit to this local hall. According to the plaque on the entrance it was rebuilt in 1943. It sits next to the site of the original Dolgarrog village which was deluged in 1925 as a result of the dam above breaking. 16 villagers lost their lives and it is said that many more would have done had they not been in the local cinema (presumably the one that predates this building).
Access is easy. There's not a whole lot to see inside, much of the building covered in garish coloured paint. The original entrance doors and 1 remaining glass panel is interesting. All of the projection equipment is completely gone.
This plaque nearby marks a memorial to the Dolgarrog disaster. The dam that burst is called Eigiau - I'm sure I saw a report on here once but can't find it now.