I think a good start would be obligatory smoke alarms to at least alert the fire service quicker, along with more stringent requirements (that are actually enforced) to have fire extinguishers. Maybe extend it to a requirement to have proper fire retardant materials within the construction, i.e. fire doors, fire retardant walls/ceilings, etc to at least try to slow down the spread to other parts of the building.
I still see shops and offices with those dangerous polystyrene ceiling tiles - I have no doubt at all there'll be some vape shops with those still on the shop ceiling.
The removal of the legal requirement for the fire service to check commercial buildings around 30 years ago was insane. Before then, virtually every business would get a fire service visit every few years. But since the law was changed and it became the business owners' own responsibility to self-police their premises for fire safety, it's inevitable that some simply won't bother and there's no one forcing them to do - it's only after an incident that there could be a prosecution for not complying with fire safety laws as no one is checking otherwise.
But the crux of any changes would have to be that they ARE properly inspected. At the moment, it's very lax, whether it's H&S, or tax, or employment, or trading standards etc - the "dodgy" shops are getting away with it because the checking/inspection regimes of all such bodies are very lax.