When you see 1000s of troops marching in unison, they may look intimidating, then think how well trained are they, ypu can train people to march in unison but it says nothing about their ability to fight and conduct operations on the battle field, in a modern context.
The British army is much smaller, made up of people who have signed up and not been conscripted, so they want to be there. They are very well trained and have to be the best to stay in.
As we have seen with russian conscripts on the front line they are poorly trained and just cannon fodder. Most seem to be trying to desert to save their own skins (which is understandable). Time will tell if N Korea is a help or a hindrance.