Re: Not so much public ownership but public wealth creation
I'm not sure that the 30s private housing boom is relevant to the council house building activity. Over 1 million council houses were built in the inter war years. That's not a small event.
Regarding the NHS, I don't think there was anything simple about the nationalisation of existing facilities. Not sure what data would suffice. My parents said it was the biggest change in society in their lives (and they'd just lived through a war). Before they used to get treatment for free, and handed in rabbits for the doctor once or twice a year.
I picked up on council housing and the NHS, but I think there were other publicly financed investments in the 20th century that may have had an impact on wealth. Road building, education, electrification, gas grid, ports authorities, whatever. My image of this is that it increased steadily in the early part of the 20th century, and accelerated after WW2. I can wave my hands like any economist and say this was the cause of reduced wealth inequality. I'm hoping you can do better.