I just received my TM P226 today that the seller shipped RM 1st class signed for. He just told the post office it was a toy ffs.
The problem with this is if it gets scanned/checked, guns toy or not are restricted items and do get confiscated.
I believe the correct way to send them is Parcel force 48hr. As long as you state that it is an airsoft gun. Their T&C's allow you to ship them.