That may have been the case for the early years after 1945. In the 1950's, business was blooming, especially for the M/C manufactureres. AMC for instance invested huge amounts of money into new semi-automatic machines and new buildings in the late 50's. I believe Norton/Triumph did the same.Britain was bankrupt after WWII. It had used everything it had, then borrowed more. There was no debt relief, grants or charitable investment for the Victor. Industry had to make do. No money to invest in tooling and infrastructure.
We have to look elsewhere. I think the main reason for the industrial decline was lack of leadership, extreme conservatism, professional incompetence, and a demotivated workforce by the social climate.
At the same time, the japanese factories were able to modernize, underpinned by selling cheap transports (mopeds) to millions of Asian buyers. Profits per unit may not have been much, but when you sell 50 million units, the revenue is still substantial, allowing (and necessitating) rational production methods, which paved the way for building modern big bikes at very competitive prices. At the same time, the European manufactureres lost their home markets (this happened in the UK as well as in Germany, France, Italy and Sweden). The "japanese train" of market success was impossible to compete against. The European societies failed - they liked the foreign goods so well, they deserted their own producers. The m/c press is also to blame. They were unprefessional and partial to domestic manufacturers, which made the manufacturers complacent.
- Knut