Hi! Unfortunately, in the UK there is currently no supported way to watch Microsoft Movies & TV purchases directly on an Android phone. Microsoft confirms that previously purchased content remains playable through the Movies & TV app on Windows and Xbox devices, but purchases cannot be transferred directly to another provider. Since Movies Anywhere is limited to U.S. accounts, it is not available as a UK option.
The best available option is to use a Windows device or an Xbox signed in with the same Microsoft account used for the purchase.