Since I used to deal with "abuse" complaints aimed at people who had left their wireless networks unsecured, and remembering the amount of work in persuading them that their unsecure wireless network was allowing people to abuse their connection (I still laugh at the person who claimed there was no-one else with access to his house to plug a cable into his wireless router - he eventually clicked, took a while ), I'd suggest popping round to your neighbour and letting him know...