yougov also repeatedly reports that x% of the UK population want COVID-19 restrictions to continue indefinitely, along with the closure of nightclubs. You'll forgive me if I don't treat yougov as the main source of UK sentiment
Sure, almost all off-the-shelf polling is rather bad these days, but they did their job as well as you can reasonably expect.
That said, modern polling uses a host of techniques and is of course not tied to landlines. Companies use access panels of available participants, f2f sampling (walking to random people's houses, but that's expensive of course), and in particular statistics such as poststratification.