The UK needs to do both. It needs to allow denser development, but that isn't enough. It is also possible to expand the green belt without causing suburban sprawl.
There's not one green belt. There are a number of green belts, typically constricting our biggest economic centres, but the spaces between allow development.
This leads to situations like Oxford where people working in the university that gave the city its current fame can't afford to live in it. Instead they live in suburban towns outside of Oxford's green belt and commute in - through it. Ironically, there is now an incentive for the same number of people to sprawl over a larger area, requiring more railways, roads and parking. Many locals in Oxford's new sprawl expect a non-existent greenbelt to protect their areas and are left disappointed.
The real rub is that England lacks Scotland's right to roam. So protecting all this green land doesn't even give us the right to walk in it. Only to gaze from a passing window.
