If a company is owned by a foreign government, it should be barred from industries that impact on security. This is not a vague definition, this is something that we have thrown significant resources into identifying. The interests that the Chicoms currently have should be removed from their possession.
I find it difficult to believe that you don't have your own reservations about what foreign governments may own. Likely our difference is in the who and what. And the what depends on the who - some things are far risker in the hands of a culture that glorifies suicide murderer than in the hands of cold socialists who believe oblivion awaits them upon death. Some things are riskier in the hands of those who have nothing to retaliate against than those who do.
The guideline is very simple and common sense. You don't put anybody who could reasonably be suspected in having an interest in doing us damage in a position to do so.
If it were, Doncasters would have known, prior to the sale, that this facility would have to be split off and sold to someone not on the list of badboys.