Ok … it's back and running, here is what I did ….
1. Renamed the game folder: "C:\Program Files (x86)\1C Game Studios\IL-2 Sturmovik Battle of Stalingrad" to "C:\Program Files (x86)\1C Game Studios\IL-2 Sturmovik Battle of Stalingrad - Orig"
2. Went to my profile here: https://il2sturmovik.com/download/ selected download and went through the process of installing the installer and letting it re-download and install everything again from scratch.
3. Copied over my Inputs folder from the renamed installation folder.
It now loads …. haven't gone any further but it appears to be fine.
Hope that helps.