Work in progress after my earlier postings.
First I went into iCloud Control Panel on the PC and stopped iCloud synchronisation of Calendars and Contacts via iCloud, and then did the same in "Settings" > "iCloud" on both the iPad and the iPhone. I didn't want iCloud changing the data as I did the corrections.
Then - All the next work was done in Outlook.
Contacts
I selected all the contacts in the "Contacts in iCloud" and copied all of them to "Contacts" in "My Contacts". Then I manually deleted all duplicates in "Contacts" - straightforward but a long time to complete.
Calendars
I copied the "Calendar in iCloud" into "My Calendars" which created a new Calendar "Calendar1". This was for back up in case anything went wrong (maybe I'm paranoid but better safe then sorry).
Then I changed the view of the "Calendar in iCloud" folder to "Categories", the selected all (CTL-A), and copied all the entries back into "Calendar" in "My Calendars". This populated the Outlook Calendar again. Then manual work of hercules to delete the duplicates, set the categories, and reinstall holidays.
Then into iTunes and set the sync for both my iPad and iPhone to sync Contacts and Calendars, and to "replace items with Outlook entries" for the next sync on both the iPad and iPhone .
Then ran Sync and at the end - all 3 devices show the same data and are correct. I'm back where I was before iCloud!
Remaining work is to delete the iCloud Calendars and Contacts, since they are just wasting space but they don't affect any of my 'real' data. I had been to an Apple Store "Genius Bar" when I first had a problem, but thye were all new to iCloud and couldn't help much, although they showed me that I could delete the iCloud entries by, I think, logging on to iCloud and clicking on, say, Calendars and selecting delete from the pop-up menu, but when I tried this from my PC it doesn't give me a "delete" option in the pop-up menu. Maybe my memory of what they showed me is wrong, or maybe it only works when you access iCloud from a Mac? I'll have to contact them again - unless anybody has any other ideas???
Anyway - I hope this helps anybody else in the same position as I was... But it's an awful lot of work......