OK Gents, I think there's some progress.
I noticed, just before the repair option appeared, that there was the briefest of appearances of the screen inviting fresh installation or repair.
I booted from the CD once more and just managed to stop proceedings at the correct spot. The machine is now about 40% of the way through copying files.
I can't emphasise how brief was the appearance of the options screen.
Thanks again, chaps.
Now that is strange, sounds to me like there's something not quite right with the keyboard, a sticky key or something, so it jumps straight to the repair console instead of giving you the option you found. That would also explain the problem with the WINDOWS admin password (NOT THE BIOS ADMIN PASSWORD) as the console would "see" something so what you think of as a blank bit of the screen isn't really because of that sort of issue.