What I said earlier was

"The UK firearms laws are so straitforward and simple to understand that that might well be the case, or not!!! I bet if you asked a dozen different FEOs you would get as many different answers. "

There was a stall at last year's gunshow selling a whole selection of old mods as paperweights. So yes you probably could have a mod sent through the post provided you had no intention of using it on a firearms. I never said any of it makes sense!!