This is par for the course for UA transatlantic, where business award availability always has been very sparse compared with both economy and first. They do occasionally pop up, but not that often.

The if you're not prepared to pony up the extra miles (2.5x instead of 1.5x) to go in F (and if you do you'll get any UA connecting flights in the USA in F too), then you may well have to look for other carriers and routes.