Okay I managed to get past that and booted into ubuntu from cd. Ran a disc check from there, but it didn’t find anything.

So the I put the disc on a usb-sata converter thing that I had kicking about, and ran chkdsk on it - it found errors and then reached a point where the message was 'insufficient disc space to correct errors in index $ S11 of file 9.

Currently running Malwarebytes on it. Bit slow because USB!