Couldn't uninstall add-ins, but have solved the problem. In MC went to Tasks/Settings/General/Automatic Download Options, set that up and selected Download Now. When it had finished the Netflix tile showed up and I installed that add-in directly from MC by clicking on the tile.
All works fine now including the original add-ins from MCE Software.
I don't know whether this incident was peculiar to my upgrade or whether this is a common situation unrelated to the MCE Software add-in.