There is an easy solution:
1) Develop a small TSR program which is copied to every PC in the known / unknown UK Govt/Civil Service "system".
Each person then runs the TSR, that basically copies all their data and installed programs to their own account on the "govt cloud" (a suitable resourced central server housed in some bomb-proof, idiot-proof, hacker-proof building, somewhere near GCHQ
TSR then deletes and then overwrites everything on the local HDD (using suitably defined c:/del *.*" command).
TSR terminates with display saying "Please turn off this machine and dial 0800 xxxxx to arrange it's collection/disposal).
2) Send everyone a Raspberry Pi 4, with a pre-written SD card carefully superglued into it's socket.
3) Users can then boot the Pi and access their data on their own account via the cloud...
All non-Pi 4 machines can then be scrapped, all data is on the cloud (and suitably protected from being hacked)...and Raspberry Foundation gets a nice big order.
And think of all the "good" coming from this, as a Pi 4 is more energy efficient than an old workhorse PC - so we help to save the planet too.
And the main outcome? There will be a specific number of Pi 4's in use. One line on a spreadsheet to then give to HM Govt saying "problem sorted".