I agree it is strange behaviour.
The house next door was empty and for sale when I moved in. The first time I saw my new neighbour I was surprised because the wooden blinds were still up, and every time I walked by the downstairs light was on, just as it had been when the house was for sale. I said hello, but was blanked. The next time I saw him I said hello again, and was blanked again. For the next two or three weeks I kept my music turned down low, just in case my music had been annoying him. I ought to stress that my separates are not connected and I have been using an old ghetto-blaster, which is always used at a low volume due to sound distortion, so it is quite unlikely anyway that my music would have caused much of a problem, although as I said before, the walls are single-brick thickness and do transmit a fair bit of noise. Having said that, I had been living next to an empty house since September and was unaware of this design flaw having had no neighbours.
During this period of keeping my head down and hoping that the situation would blow over things in fact took a severe turn for the worse, with an increasing campaign of noise directed against me. Bangs on the wall, door slamming, assorted scrapings, electrical appliances, etc, aimed at depriving me of sleep. Each time I have found a coping startegy for the latest method, a new one has been devised when they figured out I had overcome the last one.
If I had caused a problem, I would have expected the guy to come round and say something. I am a reasonable person, and if someone makes a polite and reasonable request I will happily attempt to find a compromise. I believe I am approachable inasmuch as I am not built like a brick shithouse (ten stone, wet), and I say hello to any neighbours I pass on the front.
I do get the impression that they may be whizz-heads to do what they are doing, or they may just take it in shifts. It is a couple next door, with some ever present dole-wallah mates. Nothing against dole-wallahs, I’ve been there myself in the past. I believe the friends have a base quite nearby.
There are other imaginable scenarios: maybe they want to drive me out so their mates can rent the house, or perhaps it is an inter-landlord rivalry; but in the end you can think too much about such things.

PS – GENERAL LIGHTING, don’t know how often you check these things, but I have added a belated message of thanks to the GPS/satnav thread, and sent you a PM thanking you also. I only became aware of the article the other day when I read your PM informing me you had posted it.