"Germany and Japan did well because their special interest groups were shattered by military defeat. When new labor unions formed in Germany and Japan, they tended to be very broad-based and therefore had an incentive in the overall welfare of their societies.
'Great Britain, the major nation with the longest immunity from dictatorship, invasion, and revolution, has had in this century a lower rate of growth than other large, developed democracies. Britain has [a] powerful network of special-interest organizations. The number and power of its trade unions need no description.' " (2nd quote written pre-Thatcher)
Britain also rebuilt but at a slower rate. The point is the longer a society remains (politically?) stable the more cruft it accumulates, like the dirty copper bottom of a long sailing ship.
Think of the amount that the UK and US spend on expensive weapons systems, compounded over that period of time.
It's not really surprising, given those additional funds that Germany was able to do so well. I can't speak at all to Japan, since they have had their own problems.