10-15% in the opposite direction. That is I stated they earn 10-15% more.

33% less equates to them earning roughly 50% more. The difference between 10-15% and 50% is huge!

(trivial example, if someone is earning £100,000, then someone earning 33% less makes £66,666. But Someone earning £100,000 makes 50% more than someone making £66,666)

You said that UK's salaries are 2/3 of the Germany ones, but this doesn't mean that the Germany ones are 1/3 more, they are 1/2 (or 50%) more. That's pretty far from 10-15%.

Oh sorry, then I didn't maths properly. I always forget about the asymmetry of fractions

No problem, it's a pretty common math/statistics trap that gets way more people than it should.