UK steel production is still at an odd quandry because the raw materials are not secure. Virgin steel needs iron ore and coal and the mining of either of these is essentially outlawed in the UK. In other words for every tonne of UK steel we would need to import tonnes of raw materials from abroad which sort of defeats the point.
It's a step in the right direction but it's a mess, it's like saying we need to build our own cars for our own security whilst we import every single part for those cars from elsewhere. It's good to protect jobs and skills but in terms of security it doesn't really make any difference whilst we cannot produce the entire supply chain ourselves.
Basically if war did break out then we're screwed anyway. We don't have the capacity to build defence products at a mass war scale let alone could we scale up steel production for those products so the security argument is very weak. In terms of supplier reliability/security a lot of our steel comes from Europe and if they go down we will too.
Just think the UK is currently building the next generation of nuclear ICBM submarines. We're getting 4 of them, they're only costing £30bn and it's only going to take 15-20 years to get them into service. The Germans built 1,200 submarines in WW2 and they lost. That was obviously very different times but war scaling is an impossible challenge for British industry, luckily the same problem exists for the Russians however they're getting more practice.