Cut outs again on mobile broadband but only in summer?

I moved here last June, was strong browsing on phone but the wifi signal on phone and dongle for tethering kept outright vanishing and even when it worked I got slow speeds.

Wifi signal even on landline router was bad though so I assumed old building but then a old block of flats opposite mine was demolished and tethering worked perfect, fast speed and wifi never dropped out(though home wifi was still weak in bedrooms).

Been using a dongle in last few days because I am away from home a bit and whenever I use it at home I have a constant wifi signal but it seems weaker, but the actual connection keeps dropping as in the wifi is solid but it becomes limited, I get a few minutes of ok, then about 10 minutes of nothing.

I would of thought that it would be better and not worse in summer as winter has more lights on, heating on and the neighbours are out of the house far more often so less electronics on.

So what is going on?

Lights, heating and other electricals produce little interference in the 2.4GHz band

Your problem is most likely down to other Wi-Fi networks, and with open windows or the changing angle you are seeing different interference patterns. Plus if walls are dry other signals will get through a bit easier.