FAA the way to go
In the 90s I decided I needed another string to my bow.. Got the FAA question and answer book airfreighted over to Europe.. read it twice. Flew to Las Vegas, started my twin training and asked about flight planning fuel calculations which I didn't understand..easy learn the answers ..only 7 for your part..three days after arriving I flew to Phoenix took the test..96%- pass 70%.eight days after arriving in Vegas I passed my FAA check ride.
word of warning..in those days the book covered ATPL jets..Atpl prop..choppers and flight dispatcher..the last three categories not needed.
Standard much lower than UK mid 70s