If this is the only effort, it's weak. Better to also (or instead) tax each box by another 20 pounds. Kids don't have that money. They'll find other things to do.
Vaping is a joke, they stuck the addictive chemical (nicotine) in it and now they are hooked on vaping. Let them sell vaping goods but they shouldn't be allowed to add nicotine to them.
Given that for most it's a less harmful alternative to smoking that makes zero sense. Aside from it's addictive properties nicotine is on about the same level as caffeine in terms of damage.
It's already prohibitively taxed to be around £12-15 for a 20 pack. There are 4 corner stores within a 5 minute walk of my house that do them under the counter for a fiver, and you can bet they don't care about IDs either