It's utterly bogus. The lion's share (£176bn) of your £380bn comes from, according to your own report - instantly slashing "Working Time Directive, Climate Change and Renewable Package" etc - with £132bn coming from instant FTAs.
- the report's a joke.
The authors are also claiming that their polling data show Brits don't want an extension, whereas their own data show more Brits than not think it beneficial:
Rather, it’s designed to be unchecked easy disinformation for tabloid press to regurgitate... for social media to circulate.
Remedy? Report the press articles & ‘report’ to Full Fact: