DHC is roughly 1.5x as strong
and parttime- the difference between codeine and white lightning, is that as a P medicine codeine linctus is legally to be sold at the discretion of the pharmacist. they can say no for any reason, in the same way off licenses can say no to someone asking for alcohol (and legally they *must* do so if they are already drunk as many Shitening purchasers would be.)
the reason why one stops you and the other doesn't is that pharmacists are highly educated health professionals who could lose a well-paid job if they act illegally or unethically, and inspections on chemists do happen. while there are no RSPGB going around offies and checking who they sell their 9% lager and white cider to, and most people who work there are on low pay and not so worried about people's health.