Thanks all for the help.
The External drive usually sits on my desktop but I was using my laaptop to look for a photo when I realised my photos (all of them) were missing.
I searched for the word photo (I never realised how many things with photo in the title I had) but none of the photos themselves. So I knew a couple of file names so I ran a search fo r those too. Alas nothing.
Last night (quite late I installed Zero Assumptioon on to the desktop PC (where the External usually resides) and ran the Zero Assumption over night.
This morning THE PHOTOS ARE THERE
BUT
It looks like there so many I will have to go and buy another 500GB or a 1 TB External drive to copy them on to. At least I know they are there and I can recover them ... They are all going to need renaming, sorting in to the correct dates and in the correct order.
Moral of this is: If you use a external drive and you cannot find the files on one PC .. try it on another .. you may find them there!
I can VERY much recommend Zero Assumption as it is FREE for image recovery.