Far more than 50%. A year ago it was normal for suppliers to pay about £50 per MWh (consumers of course end up paying a little more, this is a for-profit business in most cases) and today you're being charged maybe £200 per MWh.
In one peak period yesterday it went to £365 per MWh and I'd expect the same today. Unlike in Texas, UK consumer electricity firms have to apply the price cap, so while you can get electricity for £0 in the middle of the night sometimes (though not so much recently) that full £365 wasn't passed on to you, but of course the financial strain of such offerings under current situations means these firms go bankrupt, and sooner or later the government will end up having to fix it.
Everything paying Contract for Difference subsidies would be above water now, not just the nuclear plant, the most expensive older wind farms are actually net profitable for the government via its wholly owned energy subsidy company. If your wind farm is guaranteed £150 per MWh, and electricity sells for £365 per MWh, you're paying the government £215 per MWh of the income from selling wind power - if you put up a newer, cheaper farm and only secured £80 per MWh, that's £285 per MWh you're giving the government, and your investors are probably re-assessing their appetite for risk accordingly, if they'd just said "Fuck it, we'll build it without a subsidy" that £285 per MWh is profit.
