Thanks again for all the help you've provided.

I connected with Microsoft this morning. Initially the support guy thought some derivative license files left over from the free version of 365 might have been preventing the subscribed version to be installed correctly. However, he then stated my profile had been corrupted, so he created a brand new profile to install 365 Personal against which then allowed me to open and use Excel, Word, Powerpoint etc.

Odd! But all sorted now.

Many thanks for spending time investigating.

Kind regards,

Ben.