I would have bet on this being a prison, but apparently it’s Prestatyn Holiday Camp circa 1952.
According to British Holiday Camps: A Brief History, it was “[d]esigned and built by the LMS Railway & Thomas Cook in 1939. Noted for its wonderful architecture the camp was later sold to Pontins and renamed ‘Tower Beach’ but was eventually closed in the 1980s.”
Wonderful architecture, eh? But check out UK Holiday Camps of the ’60s and ’70s for some great vintage ads including this one for Westward Ho! Holiday Camp in Devon: