Changing channel?

[#1]

Contracted for 40mb, with the usual openreach/technicolor combination of kit.
Sometimes recently, however, everything has slowed right down, but then perks up later. No pattern detected yet, but a neighbour might be the culprit. Someone has suggested changing to a less used channel might reduce any local contention (if that's what is causing it).
How would I do that please?

[#2]

This should help  
Edited to add - you could also try using this or something like it to scan for the least congested channel in your locality.

[#3]

I'm presuming it's all ok with wired? If so, then changing the channels may well help. See the link above for details.

[#4]

Or if you have an Android phone, get this free app "Wifi Analyzer" by Farproc on the play store at https://play.google.com/store/apps/details?id=com.farproc.wifi.analyzer&hl=en_GB
Then you can walk about the house checking the signal strengths in any room without trying to balance a laptop.

[#5]

Thanks guys!
Tony, when the prob occurs it seems to affect both a wired laptop and this Ethernet desktop.
Will see if it persists and if so will adopt your suggestions.

[#6]

It's not a wifi problem then, seeing as it's also affecting wired devices. It's still worth a quick scan with a wifi analysing program though, just to make sure your wireless is on the least busy channel anyway.
If there doesn't seem to be a pattern to the slowdowns, all I can suggest is keeping a log of when they do happen to see if there is in fact a pattern that is not immediately obvious. Good luck, intermittent problems can be a real pain to diagnose.