Sorry to hear of your visits by The Arseholes of Humanity.
The garage door idea is a beauty, as is the Gun.... and the dog. The only one that wont make you the criminal is the dog though....
Being a Shotgun and Firearms license holder, with a cabinet full of guns, it would be nice to have the same rules as the yanks under such circumstances.... but we will be the one inside after the incident and the scrote will probably get a holiday to the Maldives and a new Porsche to help him get over his trauma.
I think all the solutions offered by everyone are the best way... you can get those PIR operated video camera units for under £100 (seen them in my local gun shop) for times when no one is at home and they are easily hidden so the scum wont see them.
Finally... an old Forest chap, sadly deceased, had a wonderful idea for stopping people tampering with the Pheasant pens he looked after.
Sharpened 4" Nails hammered through planks, sharp end up and hidden under leaves.
Certainly caught the two blokes who were doing it, but caused him a whole world of aggro from Plod and the courts.
Get a house sitter for your hols and have a good one.
PP