Doesn’t the UK have access to youtube?
You can make a shot gun with two lengths of pipe, a screw, and a few other parts for about $7. https://www.youtube.com/watch?v=n1wV3lmbSv4
Got some more time and have something like a drill press, some files, and a vice? You can make something much more complicated.
ETA - I didn’t mean to reply to you, openfly.
