On the lack of fire extinguishers in the UK, the Get Out, Stay Out, call the Fire Brigade advice is probably appropriate. Not only are folks susceptible to smoke inhalation and failing to evac others, but in the US something like only 1 in 10 have ever actually fired off an extinguisher before they actually need to. It's not rocket science, but there's some chance that the extinguisher could be past its expiration, or they may seriously underestimate it's firefighting capacity, or not follow the PASS guidance. And I expect the fire brigade is almost immediately on scene once alerted, mitigating damage / loss. Modulo the 'in event of a greater emergency' scenario.

That said, everyone should practice with an extinguisher - you get to burn things, and put them out, what could be more fun. I used a 5 lb CO2 model approaching its 5 year expiration to have my wife and kids practice putting out some contained fires in the backyard. A little messy, but a good time was had by all.