I am losing my wifi connection in the afternoons, presumably when the nieghbours' kids get home from school.

I have a number of wifi connections show up on my network item and running sudo iwlist scan give me a list of wireless devices on various channels including channels 1, 6 and 11.

No matter which channel I set my wireless router to it seems to be drowned out by my neighbours.

Is there anything I can do? Short of taking out my shotgun? (Just kidding!)

How do their relative signal strengths compare to your own?
Have you compared them in the morning vs afternoon?

There could be other devices like cordless telephones that work on the same frequency that have higher output power which is causing interference vs other networks. Are you personally using any cordless devices in the afternoon vs morning?

No, no cordless devices.

As far as I can see the signal strengths of the three main wifi devices are similar to mine (although my own device is in another room).

After struggling repeatedly and changing the channel on the router (which allows a connection for around 5 to about ten minutes), I have rebooted and am now up.

I am currently on channel 6 and another router is on channel 11. A third router is showing up on my system tray network icon but doesn't show up on iwlist scan. An additional router which I see quite often does not appear to be on at the moment (which may account for the fact that I currently have a decent connection).

I am in a detached house in a good neighbourhood (which probably accounts the power of their devices).

To determine, you'd need a device that is designed to scan that region of bandwidth. You will only be able to detect wi-fi in any windows/linux app I'd guess. Someone may have some hidden channels or some kids doing hacking.

I agree that any number of other emi/rfi sources exist.

A more simple test might be to go to a different band or borrow someone's router just to see if that may help.

I never use wireless myself unless there is no other solution.

Lots. Its just that most of it won't work.... Mind you, often the shotgun only has temporary positive effects.

The afternoons bit is a bit mysterious - possibly something like a game console? You wouldn't expect them to have the microwave going for extended periods (5 oe 10 minutes yes, hours on end, no), It could be bluetooth, which wouldn't show up on iwlist, IIRC.

Switching to the 5 GHz ('wireless A') band would be a good idea, as that band is less polluted with random interference, but probably isn't something that you can easily do.

No adjustable antennas or external antenna option on your router? does it have 'n' (if it is an early n device, and particularly one with multiple antennas, a firmware update has a chance of making performance a few dB better, on average, which may make the difference...or maybe it won't)? can you re-position it (some positions and alignments will be better than others, but his is primarily a trial 'n error thing, so there will probably be worse positions as well as better ones).

An external directional antenna could also be positive, but you'd have to have a connection for that - many routers don't.

Collecting actual signal strength reading over the day may show up something...or, there again, it might not. for example, you might find that one channel gets particularly bad interference in the afternoons, but the rest of the day it is ok. Difficult to know until you try it.