Nialmac,
The bsa standard air rifles are wonderful" guns" made from 1919 until the start of WWII . I have 3 of them & use them for crow control in the city-no noise. A english firm P & J Springs have quite a few parts if required.One word of warning don't dry fire the gun ( ie no pellet in the loading chamber) & use the proper cylinder oil which is not oil based.

NCR