The UK has trained plenty of the Ukraine structure.
The difference there is 1. They're being invaded so they have an extreme and focussed purpose, 2. They get almost whatever they want for free (at point of sale) from NATO and other friends, 3. They had a bigger pile of (admittedly old and out of date stuff) to begin the fight with.
The downfall of the UK has been engineered over the past 35 years or so, it's not about to be turned around overnight.
I'd quite like to see a reasonable and believable energy security policy that puts generation on this island as the main priority, before taking a small part in the next cold war or pacific adventure.