I finally found a working fix for this issue. I now have a character model and am able to spawn into career mode correctly. This solution is for Steam users only, please let me know if it worked for you!
This method is slightly different to @FGEJaymz posted above.
Ensure MSFS 2024 is closed.
In the following path: “C:\Users\YOURUSERNAME\AppData\Roaming\Microsoft Flight Simulator 2024\StreamedPackages”
delete ALL the folders that start with “asobo-proceduralgeneration”. There should be 15 folders to delete in total.Turn off Steam Cloud in Steam settings.
Go into offline mode on Steam.
Navigate to where Steam.exe is located. For me it’s “S:\Program Files (x86)\Steam”
Navigate into “Program Files (x86)\Steam\userdata\STEAM ACCOUNT ID\2537590” (Find your Steam account ID by using https://steamdb.info/calculator/)
Confirm folder “2537590” has a folder in it called “remote” and a file called “remotecache.vdf”.
Delete folder “2537590”
Reboot PC
Start Steam (Keep it in OFFLINE mode)
Start MSFS 2024
When prompted, re-login to your XBOX account
When the progress bar shows at the bottom of the screen (it should get stuck on 0%) go ONLINE on Steam
From here I was prompted to create a character identity like the initial install but It crashed again when selecting my characters outfit etc.
I launched the game mulitple times and this persisted.I then turned back on Steam Cloud with the game closed and when it prompted me that there was a cloud conflict, I selected my latest local data.
After this I relaunched the sim another couple of times and then I suddenly had a character that was able to be customised.