Some wifi routers are designed to search for a free channel. It may be worth selecting one channel in the settings. If you have an Android phone something like Wifi Analyzer will show you where there are no neighbouring wifi signals to set your wifi appropriately. But be aware that some kit, like Kindles, can't be set to all the European channels.
I have a wifi analyser app on my tablet and something similar on my laptop, which is how I know that my router is changing channels. My phone, laptop and Smart TV all follow the channel changes.
My router seems to be doing a bit of a dance with my neighbour's routers! My nearest neighbour's router signal is fairly strong and there are 5 or 6 weaker ones. My router changes to avoid the strong neighbouring channel, but theirs seems to be hopping about too, probably to avoid another neighbour. I am end terrace so I only really have that one to worry about. I'll fix it and see if their router is smart enough to stay clear of my channel!
I have been looking at the lights on the router and it seems that the broadband signal itself is also getting interrupted, I'll get in touch with Plusnet and see if they can find anything wrong with the connection.