Very few criminals in the UK have guns, especially not petty criminals as they are so difficult to get hold of. Most burglars are just guys that want to grab some stuff then run off, they are rarely armed with anything. However, kitchen knives are often grabbed by panicing burglars. In most cases self defence techniques can be used, as burglars do not go looking for a fight. Just shouting at them to fuck off will often make them take off, they aren't the mafia, just cowardly twats who want some money.