Never knew that Dudley Zoo was used as a depot(Black Country though not Birmingham), there was a company in based in Dudley that boxed motorcycles for shipping abroad, SGB Ltd (Stourbridge Glazed Brick) I think they boxed Triumph 3HWs.
Ketley is only about 2 miles from the RAOC Central Ordnance Depot, Donnington, so it could have been an outlying store. It also looks as if there was an R.N. Armament Depot there located at the Wrekin Foundry. In the run-up to the liberation of Europe, any suitable buildings were used for storage.