Thanks for everyone's help. I've managed to get back to a legacy boot with Windows updates working and Bitlocker encryption. Here's what I did, in case anyone else manages to get themselves into the...

Thanks.
So far I've cloned the laptop's SSD to a spare HDD using Macrium (I gather this disables Bitlocker in the clone). I plan to put the cloned HDD into my laptop and follow the instructions to...

I'm planning on getting to a proper Legacy-MBR system first, as that seems quickest and lowest risk. Once I'm happy with that and I can get the Windows 10 updates again I'll back it all up and try...

Thanks for everyone’s help. I’ll try the suggested approach to switching back to legacy boot when I have time over the next couple of days and I’ll report back.

Thanks. I like the sound of this approach. I can worry about moving to UEFI in the future, if ever. As there’s already a system reserved NTFS partition, can I skip the formatting step? That way I can...

Could you explain what this will do please?

It doesn’t look like the free version of Partition Wizard will convert an OS disk.

Sorry, I’m new here. What’s the Powershell code for?

Thanks. Partition Wizard sounds worth a try. I have a spare HDD which I can clone to as a backup if it doesn’t work. I’m a bit concerned that it might not be possible to cleanly convert the messed-up...

Thanks for your quick reply. Is there no route to getting to a consistent legacy boot, or UEFI , without a reinstall? It would take me forever to reinstall all my programs and resync my cloud data if...

Hi

When Windows 10 ran its automatic update I got a message "Windows can't be installed because this PC has an unsupported disk layout for UEFI firmware". I think this is probably my own fault - I...