It's for the silliest reason as well, we stopped including psuedoephedrine in OTC cold meds because Theresa May government were concerned about people using it to make meth, with no evidence that people in the UK were using it to make meth...
You can still get pseudoephedrine but you have to request it at the pharmacy, as it's a pharmacy medication now.
So in reality no difference in terms of accessing it, if you really wanted to make meth, just means that most people can't get an effective decongestant when they're on their way to work...