They are the new plan...
I have looked at satellite maps of cities like Leeds, Manchester, Birmingham, Bristol and others, and there are hectares of ex-industrial sites within them sitting unused.
These places already have all utilities in place - electricity, gas, water, sewage, transport - and we need to use them. Clean them up and get building!
What we do not need is to rip up arable land for out of town commuter dormitories or solar farms. The sites I have mentioned are only a stone's throw from where the work is. They could revitalise some city and town centres, or is that too simple?