I’m finally back in the air in MSFS 2020 - turns out a corrupted fs.base.nav file (which had Write access .XML files within)
Anyone freezing on half way along (just after Checking for Updates) blue bar on Greenwich screen should go to Folder; Official - OneStore - and delete fs.base.nav.
Restart the PC and start MSFS 2020. You will have to download that file agin - approx 750 meg.
Restart again when it’s done. Hope this helps.