If you look at Wikipedia (
https://en.wikipedia.org/wiki/List_of_electricity_interconnectors_in_the_United_Kingdom) you will see that we already have 7.3 GW of connector capacity, and to come, the NSeaLink to Norway at 1.4MW plus others adding up to another 9.1GW. How can that evidence allow you to claim that additional internal interconnectors can't make a difference? 2 or 3 to Scotland would make a big difference.
What really is missing (the elephant in the room) is the UK's lack of storage in the areas where we shall have power surpluses.
There are several big permitted HEP schemes in areas where there is plenty of RE but the Govt/the Grid are deliberately doing nothing about the fact that they are financially unviable because of the way the grid charges them for both importing and exporting power.
So you and I pay RE not to generate because the grid can't accept it, and we (and the planet) pay again for gas generation a bit later on when that stored RE would have been of use, and we pay a third time because that power is generated from gas (and diesel) at the peak rate when the grid is getting a bit short.
It's almost as if the system was designed to cost consumers as much as possible while hiding the real reasons.