It would in my view be preferable to use UK▸ suppliers, even at an extra cost, for several reasons.
Firstly, buying from UK suppliers will increase employment/reduce unemployment thereby reducing both the direct financial costs of unemployment benefits, and the human costs. A man earning say ?400 a week in a factory making railway equipment will have more money to spend on goods and services than the same man on benefits of less than ?100 a week.
So creating say 1,000 jobs in the railway supply chain will also create new jobs or save existing jobs in the businesses in which the wages are spent.
Secondly, UK production will keep expertise and experienced workers available in the UK, perhaps increasing future opportunities for related UK based manufacturing.
Also, there is likely to be an enviromental gain from UK manufacture. Less fuel used in transport. Almost all manufacturing uses electricity, which is "greener" in the UK than in many other places.
Unfortunately most commuters do not see like you do and currently the UK Government do not either.
NR» has to get the most economic price also it has to have supply chain reliability; it is I suspect in the case of rail supply reliability is a key factor.
The steel industry in in the UK is a victim of market forces due to it being a private sector and in the last 10 years the UK Government not willing support the industry, hiding behind government intervention would be against
EU» Law