Thanks Jason - I was reluctant to recreate a new configuration folder as I have a load of other extensions that would all have to be reinstalled.
I removed all WA extensions from Extension Manager, then reinstalled them separately in the order you suggested. After jumping thru many hoops, and one step forward, two steps backward (!!) I finally installed them all. It tried to uninstall eCart & MySQLi SBs a few times with a JS error message about "...\commands\WA_unInstall2.htm : sharematch " having no properties, but I must have hit on the right sequence in the end, as everything is working correctly now. *holding thumbs*