Is the Sig Sauer X5 C02 .177 pellet pistol threaded for suppressors ?

The only other logical way to get what you want is to find a dealer in the UK England that is willing to sell and ship you one with a threaded barrel internationally since silencers and threaded barrels are the norm over there where it's considered very rude to have a gun that makes noise to disturb the neighbors. I don't know and you go find out for yourself then let us know where and whom you got it from when you actually receive it.