BB guns or airsoft guns for the good ones.
Fall under weird laws now where you cant buy ones that look like real guns, unless you have a valid reason. Member of an airsoft site/reenactment group, film company etc
The exception being ones painted red or blue or whatever so they are not “replica imitation firearms” IE dont look real enough are not covered by this.
Whereas airguns that are waaay more powerful are find and you can just buy what you want? :?
Really depends what you want to use it for, going airsofting or just shooting at targets in the garden?
I have owned loads over the years costing £20-400 so have a bit of experience