While the unions didn't help matters, the British car industry was extremely badly managed. Strikes were not wholely brought on by 'commies', they were often jusified and the result of bad management. Also, not investing in new plant, poor designs and poor builds were the main reason for it's demise.
We still build plenty of cars, with the same workers and the same unions, just that the whole operation is better managed these days. The plants are modern and the tooling and manufacturing procedures are up to date. The models being built are better designed and what people want. More importantly, the companies continue to invest and make brave decisions such as the manufacture of the Nissan Leaf.