[ben_w]

You would have to build lots of transmission, but the losses aren't particularly significant for high voltage lines — it's only about 1000 km from the Shetland islands to Southampton, and HVDC transmission losses are quoted at 3.5% per 1,000 km. Pricing seems to be a trade secret, but the suggested numbers on the Wikipedia page for the 8 GW cross-channel link were £110M for the converter stations and £1M/km for the undersea cable.

I know that a mere back-of-the-envelope calculation isn't worth much more than the used envelope it was written on (doubly so when it is based on guesstimates of the input numbers), but that would be only £1bn for 8 GW or £4bn for 32 GW (compared to actual average usage of 31.5 GW last year), which is the kind of thing that the British government shouldn't blink at but in practice actually faffs and fails at basically all the time.

(And the sector is theoretically privatised, so this would have to become a business investment, which in turns will have potential investors ask inconvenient questions like "What's the risk we have cheaper options in 10 years that make this power line redundant? And what about those fusion reactors I keep reading about in the Sunday Times? What if Scotland becomes independent and stops selling you the electricity?")