Hi Davey
Thanks so much for that comprehensive reply ... but I think I've cracked it!! (More by accident than design given my level of knowledge about computers, but I thought I'd report back incase it helps anyone else!)
After my last post, I was scouring the forums for a solution & tried several that didn't work.
I had just done the following:
Internet Options > Advanced > Restore custom settings>OK
Then I noticed the sentence (in another post);
The problem you are having is not caused by CCleaner.
It is something that occurred on or about the same day.
... and had an 'AH HA!' moment.
(I'm not 100% sure if this would have worked on its own or if it was a combination of the two, which is why I'm including both)
I remembered that just after I installed CCleaner, in an attempt to resolve other problems I was having with my pc, I also installed 'Spyware Doctor'.
So.... I went to that programme & disabled all it's functions. Then I re-booted my computer.
Bingo!
My history has reappeared
My temporary internet files (which were also missing) have reappeared
My cookies are showing in the CCleaner 'cookie to delete / cookies to keep' list
My computer is storing cookies / passwords etc when instructed to do so (previously they were disappearing every time I closed a site, so that I had to keep re-entering them)
I'm thinking that either there was a conflict between the two programmes or that I was attributing problems caused by the Spyware programme to CCleaner. I don't know enough about computer programmes to determine which...
Anyway ... it worked for me so if anyone with similar problems has spyware protection installed it might be worth checking if there's a link.
I'm SO happy!!
Thanks again!