Is there a backup? If you're working for a company/business then I'd try
and get a backup from the IT/network people.

Is it just that the project visible property has been set to false?

Try

Windows(workbook.name).Visible=True

In the immediate window

I assume that you're M, but what the heck, I'd like to kiss you.

I am a real novice with this stuff and I had been working on it from
02h30 to 07h30 when it all went pear shaped, so you can imagine that
I was a bit "miffed".

Can you recommend/point me in the direction of an idiots guide to VBA,
so that i can try and figure some of this stuff out myself?

Sometimes it really is staring you in the face.....

it's like when turn off events early in a sub
and then stop to debug and wonder why the events don't work
suddenly . . . too funny! (too real, too).

I'll take it on the chin! However, I should point out (and
this is how novice I am) that i didn't even know there was a command
to turn the sheet to visible/invisible (or whatever the opposite of
visibkle is in VBA). I certainly didn't do it, so it must have been
the macronator or the excelxorcist as far as I'm concerned. Or maybe
just incompetence on my part.

novice? . . . no . . . a novice is someone who takes "no + [ad]
vice" . . . well, if that's not the real origin of the word, then it
should be . . . so you're not one of those . . . I might be, though,
I'll have to check with My advisors.

Well, first off, I'm wondering if you have cleaned your
code . . . and I am saying that because I had a similar problem
(when I was trying to make a macro  pretty much bombproof) which made
me work hard to figure out why a subroutine crashed when I had been
stepping thru it line by line and it crashed at a point where there
was no code showing in the VBA editor. I've become a bit obsessive
about backing up and cleaning the code I write since then, but
perhaps that's not simply a mental disorder (heheh, I hope). I
have used the freeware code cleaner found at:
http://www.appspro.com/Utilities/CodeCleaner.htm
and I have also just copied the text version of the code out to a
textfile and back . . . both seemed to be the same so I have
continued to use the AppsPro code cleaner successfully.