You're right in theory, and for sure I wouldn't be shocked if the polls nail this one, but I also wouldn't be shocked if we saw that even without fptp and const

You're right in theory, and for sure I wouldn't be shocked if the polls nail this one, but I also wouldn't be shocked if we saw that even without fptp and constituencies there's still enough of a problem with the quality of political polling in the UK to cause big mistakes. Time will tell, I guess.