Proper UK International Keyboard layout for Windows

I finally (re?)found a decent international keyboard layout for Windows for users with a UK keyboard layout.

The long and the short of it is (click to open on external site):

UK International Keyboard Layout

Download, install, and you can now easily type most characters which use an adorned latin alphabet, including the German umlauts (äöü) and, notably, the German sz (ß) character, the latter of which is unsupported using the Microsoft-supplied extended UK layout.

I completely fail to understand why Microsoft doesn’t just provide the equivalent of their excellent US International Keyboard layout for UK keyboards..