My thanks to skampydog. The site was extremely useful - how come the Sky help line don't read it?
Whether by design or accident I fixed my problem (after weeks of trying) by downloading microsoft service pack 3 for Office 2003. All now works fine, but nowhere have I read this is a requirement nor has it ever been mentioned by Sky.
I guess my problem was slightly different to Tiatadi's in that I already had a sky email address.