Hi David - and welcome to the forums.
Sorry to hear you are having problems.
Is there a Logos.log file and a LogosIndexer.log file in the logs directory?
If so, please upload them after shutting down Logos when in this "preparing" phase
If not, please enable diagnostic logging and try again - details at https://www.logos.com/support/logos5/windows/problem
Graham
My best guess is some sort of permissions problem preventing Logos 5 from updating its data files.
Please open an Explorer window to C:\Users\David Buzzacott\AppData\Local\Logos5\Data\sjvpvty2.wt3\LibraryCatalog\then delete all the files EXCEPT catalog.db
After restarting Logos 5, please upload your new LogosIndexer.log file so we can confirm that everything else is functioning correctly.