There's a Facebook group, Education Not Taxation, that's trying to collate this info. They have released a report based on Treasury, DfE and Independent School stats (so, pretty official). From their report: 127 schools have closed, and about 40k children have been displaced into the state sector (MUCH higher than estimated by the govt). The school closure numbers don't include merged schools, so there is disruption there too, that hasn't made way into the stats. The numbers are based on older data: I don't think they reflect what's been announced in the past 3 months (or more). From what I can see, there have been a lot of closures hitting the media a lot recently. I don't know who is keeping track of an up to date list.
There are significant job losses associated with the closures too - not sure how they will measure that.
On the flip side, I do not see any improvements coming to the state sector in the short to medium term, as further funding cuts there are surely going to be made - especially if the country prioritises defence and pensions over education and SEND. Any other country would offload some of the cost of education into a growing private sector to take the pressure off, but of course, ideologically, we are heading in a different direction. Those who can afford to stay in private in the elite schools will end up getting an even better education for their children, while the rest just fall further and further behind.