As a point of reference, 7% of UK GDP (2.678T USD in 2013 [1]) is roughly 187B USD. UK M3 might be a better measure, about 2.44T GBP [2]. By that calculation, a 7% haircut comes out to about 236B USD if I did my conversions correctly.
[1] http://data.worldbank.org/indicator/NY.GDP.MKTP.CD
[2] http://www.tradingeconomics.com/united-kingdom/money-supply-...