British gun control is among the strictest in the world. In general, it is an offence to have a gun of any kind unless you have a firearm certificate from the police, or you are a registered firearms dealer. To get a certificate you need a good reason to have the gun, you must satisfy character checks, and you must comply with strict conditions about storing it.
Most firearms offences carry a minimum sentence of at least five years in prison (three years if you are under 18) unless there are exceptional circumstances.
Unless you have a good reason or lawful excuse, it is an offence to have a knife (or anything else with a blade or a sharp point - except a folding pocket knife with a blade no more than three inches long).
It is an offence to have any weapon in a public place without lawful authority or a reasonable excuse. Anything made or adapted for injuring people is an offensive weapon. So is anything else that a person has with the intention of causing injury.