Green’s Dictionary of Slang

walloper n.2

[wallop n.2 ]

a hotel, a bar.

1936
19401945
1950
[UK]J. Curtis Gilt Kid 16: He would, he decided, go up into Shaftesbury Avenue and have a drink or so in one of the wallopers there.
[UK]P. Hoskins No Hiding Place! 192/2: Walloper. Public-house.