Please don't try shooting anything alive until you have refined your shooting skills.
Have you heard of Marksmanship Princials? Basically they are "rules" which if followed correctly can vastly improve your shooting, things like controlling your breathing to help your aim. They are used in the forces and it shouldn't be too difficult to find some articles.
Where in the UK are you? Maybe you can join a shooting club if you haven't already. Some coaching from someone with experience will help you no end, if there's nowhere close then go to the army cadets. I learned to shoot there, some of the instructors are brilliant and you get to use some wicked ranges. I learned to shoot well enough to represent the UK
If you need any help PM me. I am a qualified shooting instrucor and am more than happy to help