The whole point of the discussion is that there would be no single answer to that question: the number will vary by location, and by the current availability of power, because it becomes a price signal.

It would likely converge on wind farm strike prices plus margin, so about 10p/kWh .. if you lived in Scotland or near the coast. Being a localized market I would expect to see higher prices in London.

But there's also a risk of spikes. You'd probably want a regulatory guarantee of maximum prices, I think during the Texas crisis it got over $100/unit at one point.