The PHP Session Timeout issue is very annoying! So you should definitively upgrade the calendar.

Yes, if you could send me the SQL error log (via the Contact Page), that would be very helpful.
From your post I think that you are using the display1 to show upcoming events in one of your club's webpages. And I get the impression from the error message that the version of your display1.php file is not compatible with the calendar version.
When you send me the SQL error log, could you please also send me a link to the web page where the upcoming events are shown, so that I can have a look how the calendar is used.

Roel

ERROR Script: /luxcal/display1p.php - SQL query error: SQLSTATE[42S22]:
Column not found: 1054 Unknown column 'c.olapGap' in 'field list'

... and seems to be related to the displayx.php files.  The above error message is the first of many in the log file.

The PHP version running on the server is V5.5.34

Has the structure of the database tables changed i.e. more columns ?
If so, do I need to prep the tables with these new columns ?

I do make copies of database tables via phpMyAdmin in csv format.  So I haven't lost any data and have re-instated the older version (V475) for now. 

But the PHP Session Timeout issue is a BIG PROBLEM for us so am keen to upgrade asap.

I have noticed that the upgrade script has prepared the database tables (mycal_....etc ) by creating a copy of all tables and appending X at the end.

I can send the SQL error log file if required.