In a broader regional grid, where the "need to spill wind" is a net over Northern and Western Europe, and so a fraction of the "need to spill wind" in the UK alone, time-shifting Scandinavian conventional hydro-power and a modest amount of added reverse pumped hydro capacity seems like it could cope with quite a lot of storage capacity.

And then there are consumer side technologies to take advantage of a smart grid, which would all kick into top gear when "surplus" power is offered for little more than a transmission infrastructure surcharge.

I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.