For £300-£350 you can get a new hatson semi auto, multi chioke 3" and steel proofed or if you search around a "better" make second hand, there are actually a few second hand Remington 1100 on guntrader at the moment in that price range
You can use it for whatever you like, it wouldn't be welcome on a driven shoot usually but a great wildfowl or pigeon option and fine for most other things too, if you get a multi choke you may find it more flexible but 1/2 choke and changing the cartridge is the way many go...
I don't see why you think it would improve your performance though, unless its rec