Your not wrong for wanting to protect your loved ones but you have to remember that you live in old fashioned England. In the UK the law does not allow you to protect your own property by force if you find someone trespassing or attempting a burglary. If you attacked a burglar with a weapon & injured him he could sue you for assault. (& would probably win)
Its totally arse backwards but thats the way it is. I wish we were more like USA in trespassing laws but stupidly the law protects the thief's whilst on your property. So to sum up, your girlfriend & friends are right to find it a bit odd. Personally i would keep a baseball bat handy, use it to scare, but never go as far as fighting back physically as it will land you in hot water.
Tooling up like Rambo is not a good idea.