Expensive British Houses

It is an interesting idea comparing building methods across continents. A common complaint among the Brits is how expensive UK houses are, while at the same time being some of the smallest in the developed world. And why don't they have nice open plan living areas? Here is a close up of the standard cavity wall:

Yes, we do basically build 2 walls. I think that must be partly why British housing is so small and so expensive. When we were getting quotes from builders, they were using a rough estimate of between £1200-2000 per sq m! So that shows even a pokey little 100sq m house (1000 sq ft ish) is going to cost around £150-200000 to build. Add on the cost of land, in very short supply, and houses do get very expensive indeed!

As mentioned before - this wall method would not be sensible in an earthquake area! I think open plan is wanted here but rarely achieved. Partly I'm sure this is due to the cold climate, as although most if not all houses here are now centrally heated, the majority were converted after being built (ie they were designed without central heating in mind). Most of our housing dates from a time when open plan wasn't trendy either - kitchens were closed off from the living areas and separate formal dining rooms all the rage if you could afford them. This is probably the Victorians' fault! Perhaps even, wanting to emulate the aristocracy by making it seem like the food preparation was being done elsewhere by other people?
The other problem is nearly all our houses are at least 2 stories, again due to land prices, so large open areas downstairs are impossible without expensive steelwork everywhere to hold up the upper floor. As far as I understand, timber joists tend not to span more than about 3m without needing some extra support?