If the Tories are holding up pretty much completely in ultra remain parts of London then they are not surging in Brexit voting North/Midlands (have to make the national numbers ultimately add up). Either means that the constituency polls are wrong or we are not heading for the realignment that many are predicting. Judging by past history, i would be more sceptical of the constituency polls.
Quite a few of the constituency polls outside London (such as Great Grimsby and Wrexham) have been worse for Labour/better for the Tories than what the national polls are suggesting. But, as you say, constituency polls should have some significant amount of salt applied to them.
Though it's worth noting that any given series of constituency polls almost never includes enough safe seats that we can actually compare them with national polls.