Macrium Reflect did the trick.
The problem was that Windows repair thingy thought my system image was corrupted. So on the internet I found the suggestion to mount the system image VHD, then use Macrium to create a Macrium image of it. It also gives you a nicely customised version of WinPE that has a lovely gui for managing backup images. Top stuff.
So, I’ve used it to upgrade the very slow HD in my very slow Sony Vaio P series to SSD, by means of a cheap and very fast mSata SSD. The drive is so fast and the CPU so slow that the disk light flickers every so often and the CPU is flat out. So some stuff is way quicker but some stuff is still just as slow!
Managed to install W10 on it now though which is a strange and slightly frustrating experience.. With a crap hd and W7 this thing was so simple and slow I just did the bare minimum of stuff to keep it chugging along. However now I want to explore W10 and all its features, and it’s encouraging me to do all sorts of things which is making it run rather hot!