Probably the cheapest and best option is to build more wind and not care too much if it increases curtailment.
Yes, all the things mentioned should be looked into and done when it makes financial sense but "wasting wind" is much less a thing to worry about than "burning gas", and I'd rather waste wind than waste money.
Maybe if variable prices encourages energy intensive demand to shift to Scotland that will help, but that’s not quick either.
The UK is leading the world in grid interconnection and offshore wind build out (though all owned by none UK entities), so if they aren’t building quickly enough I don’t know anyone who is….