2. Polarization while not as bad as US, is larger than in past so winning in constituencies Tories won by 40 points in 2019 seems unlikely.
It’s absolutely not. In the post-war period our 2 major parties used to get 90% of the vote together and elections were usually quite close and voting patterns semi-stable. A key feature of modern British elections is how the electorate have next to no absolute loyalty to political parties, if you piss them off then they will go elsewhere. 4 years ago the Conservatives came 5th in a national election with 9% of the vote and then months later won a landslide with 44% of the vote. That’s not a stable, partisan electorate. Labour won’t be winning many constituencies with 40% Conservative majorities, but the suggestion they will is largely down to crap MRP (a consistent feature has been a flattening of party suggest, the one above has Labour’s vote falling in its safest seats despite absolutely surging in safe Tory seats).
Wasn't in past more identification as one was Tory because of where they lived, class and profession and Labour for same reason. Whereas now more ideology as you have fewer wets than in past and fewer blue collar populists so some change. But it is true UK doesn't have near the polarization like US does. In US a lot hate those of other party with a passion and many will always vote a certain way no matter what and if dislike their chosen party, they just stay home and not vote at all, not switch parties. In some ways more like rest of Europe where you are seeing more parties and combined totals of traditional much lower than historically the case.
Still like US you do have echo chambers at least when it comes to what media people read but not on television like you do in US. After all most who read Daily Mail, Sun, Telegraph, Daily Express, Times vote Conservative while most who read Guardian, Daily Mirror, and Independent vote Labour. Financial Times and Economist somewhat more diverse and a lot there vote LibDem as many who read both traditional Tories but voted Remain unlike others mentioned who mostly not only vote Tory but voted Leave in Brexit referendum.
Issue is papers aren't actually that powerful anymore. The most read papers are the two you don't even mention, the Evening Standard and the Metro, both freesheets who make every effort to appeal to everyone simultaneously - populism in its most mushy iteration. The once hugely influential Sun has collapsed in every metric, and I would not be surprised if it vanishes in the future. The Express and the Mail get by on their geriatric buyers (the Mail is also bolstered by its celeb-oriented web presence, but the politics is secondary there) but are not agenda setters in the same way they once were. The broadsheets are barely relevant at all (if they ever were) outside of their small niches.