As far as I can see the Government has been increasing the capacity for processing tests ever since the pandemic started. There were not enough NHS labs in existance and, IMHO, it would not have been possible to build all the new facilities the NHS would have needed in the time given so going to the private sector was the only way possible. Emergency plannig could never be expected to be able to cope with such an unprecidented demand either at NHS or in the private sector
Can't find a singe neat link covering the increases of Laboritory capacity but here are just a few.
https://www.england.nhs.uk/2020/03/n...-testing-labs/
https://www.rcpath.org/uploads/asset...9-Testing-NHS-
Laboratories.pdfhttps://www.medicaldevice-network.com/comment/lighthouse-labs-uk-covid-19-testing/