Help! My iCloud Account is Broken!

Some time in the early hours of the 15th August BST, something went very wrong with my primary Cloud account (and only my primary account) and its now screwed up!

• I'm unable to view or send mail with its email addresses;
  • On iOS / iPadOS it errors "Cannot Get Mail. The connection to the server failed." 
  • Adding the account to another devices as a secondary iCloud account received the same error
  • On macOS Mail it just constantly says "Checking for Mail" at the bottom of the sidebar
  • I’m unable to add the email account to third-party mail apps or services as I’m unable to generate app-specific passwords
• I can’t access iCloud at iCloud.com; It lets me log in, goes through 2FA, and the trust browser option, then says "Connection Error. iCloud encountered an error while trying to connect to the server”. It does this for every possible device / browser combination I can think of; 
  • maOS 13.5: Safari/Firefox/Chrome over both ethernet and WiFi with Private Relay both enabled and disabled.
  • Windows 11 PC: Firefox/Chrome over both ethernet and WiFi.
  • iOS 17 PB (21A5312c) on iPhone 14 Pro; Safari/Firefox/Chrome over both WiFi and Cellular with Private Relay both enabled and disabled.
  • iPadOS 17 PB (21A5312c) on iPad mini 6; Safari/Firefox/Chrome over both WiFi with Private Relay both enabled and disabled.
  • iPadOS 16.6 on iPad Pro 12.9 5th gen; Safari/Firefox/Chrome over both WiFi with Private Relay both enabled and disabled.
• I can log into appleid.apple.com with no issues.
• I’m unable to generate app-specific passwords (my existing ones were revoked when I reset my password); when I try it asks me for a name , one on the next step tells no to continue on my iOS / Mac device, direction me to a setting that doesn’t exist!
• Photos, Notes, Calendars, Reminders iCloud Drive etc. no longer sync across my devices
• iMessage appears to be the only service syncing across my devices
• 2FA requests ping to all my devices as normal
• When I go into Apple ID / iCloud settings, the bar showing the breakdown of my 2TB storage (with 153GB free) is not displaying correctly;
  • On iOS / iPadOS: The bar is proportionally filled correctly and shows Messages / Mail / Family however the amount of space usually labelled as Documents and Photos & Videos in now a single grey bar.
  • On macOS / Windows: the bar represents ~248.5GB and shows only Messages / Mail / Family, Documents and Photo & Videos are not displayed at all!
• I’m unable to sign out of iCloud on my iOS / iPadOS devices, getting the error “Could Not Sign Out. There was a problem removing this iPhone/iPad from your account. Try signing out again.”, resetting network settings has no effect.
• I was able to sign out of iCloud on my Mac, and once signed back in nothing has synced back or downloaded.
• I’m unable to turn on Password syncing on Mac. It says it requires end-to-end encryption and when toggled does nothing.
• I toggling off and back on Access iCloud Data on the Web, it toggled off fine, but won’t toggle back on instead giving error “Something went wrong. Try again”.
• When I first reset my password, I saw the option to force a sign-out of all my devices and browser sessions, and decided against it as I could lose access to my account completely. 

I have;

• Read the support article "If you can't connect or sign in to iCloud” [If you can't connect or sign in to iCloud – Apple Support (UK)]
• Contacted Apple Support via chat and was escalated to a call, they said there had been recent maintenance in iCloud services and to wait 8 hours to see it if resolved itself. At time of writing its been over 18 and still having the issue while the Apple status page show all systems green.
• Tried to search the here and find situations similar to mine, bit not found anything relevant.
• Run out of possible causes of things to try.

Help! This is a major issue, the syncing is an annoyance, but I can't be without access to my primary email address!