Willamette is is a genetic triploid, in part derived from a tetraploid Fuggle. The flavor is mild, but similar to Fuggles, as is its aroma.
US Fuggles and UK Fuggles are, as noted, the same plant genetically; there is a subtle yet noticeable difference between the two, presumably due to environmental factors. Regardless of where they are grown, Fuggles are a seeded hops variety. Seeds are dimly viewed by most brewers, so many prefer the seedless variant Willamette.
Note also that Styrian Goldings are also Fuggles.
Cheers,
Bob