[Matth]

I believe there are actually 13 wireless LAN channels in the UK, but most equipment doesn't let you select >11.
Those channels overlap as well, so you cannot use adjacent channels - some say that 1, 6, 11 (USA spec) are the only usable channels - if things are tight, try to get at least 2 channels away from an occupied one. And that is really too close even then - If you only have a 1-11 channel selection, setting the videosender to it's highest may move it above 11.

1, 4, 7, 11 is a compromise 4 channel usage, but range will be degraded - but if 1, 6 and 11 are all in use, try to persuade whoever is using 6 to move to 7, as if you slot into 4, it'll hurt their performance less than if they stay on 6.

Channel 9 and adjacent suffer severely/moderately from Microwave oven interference.

The usual default is 11, it seems.

Basically, if you have a video sender on a low channel, set yopur Wifi to a high one, or the reverse.

It can be done, but there isn't much room for anything else in the locality ... a neighbouring WiFi network or video sender will leave you struggling to fit an additional device into the channel allocation.