Assuming that guy was really scouting you out and not getting cucked by his satnav... the reason he's scouting out houses is to find out when you're not home. So even if you're lucky enough to catch him red handed, and you can actually get to your gun, and it's the 0,1% of that case where that guy wasn't just going to run either way... You still live in the UK, so you're still fucked. https://en.wikipedia.org/wiki/Tony_Martin_(farmer)