Getting a few PM's about what to do when you get to Manc Airport, in the interest of me going for a beer, here's what I did.
I went straight to the checking desk and handed over the passport, they knew we had firearms and called the border police to come and check them. The guy behind the desk fills in a form and asks for your serial number on the gun, make sure you have this handy. Border police came, checked the guns and took them away. Our cases got weighed and then we took them around the corner to Oversized Luggage, not sure why but I'm guessing it's because they have pellets in them and they want to do a deeper scan.
DO NOT PUT YOUR PELLETS WITH YOUR GUN.
The whole process took about an hour.
If you know where to look i've done a couple of videos on stuff while I've been here.