I had weird dreams like this about my modified 1.8t mkiv - came true one Monday morning when I found the whole R32 interior had been stolen.
Our street is quiet, but overlooked by 6-7 other houses. It was nearly unbelievable!
Anyhow, back to topic - I think it's very hard to stop some devious lowlife who's hell bent on your car or its parts. Still wonder to the day if I had heard my car being broken into, would they have stopped & scarpered if I came out into the street, or would they smacked me one & continued regardless.
I had a Clifford proximity sensor on a mk3 Golf - it was a nightmare. Always going off in the rain, when the postman walked past, etc. NOT something that would encourage your neighbours to check out, if it's sounding out!
Best I can advise - a CCTV system and a tracking device. CCTV may put off an opportunist, or give a few clues of any strange activity if a professional has been after it...
