WHEN you talk to Herman about what he's been doing lately, you fnd that he has to pause and think a bit. "Let's see, was that in Australia? Or was it America? No, it must have been Japan, 'cos it happened after I bought that fab Japanese dance mask to put on my wall at home ..."     Herman has every right to be a trifle confused. As you read this page, he will be in America again, if all plans go well. "Fingers crossed," says Herman with that wide grin he never loses.     This will be his fourth visit to America, and the odd thing is that over there Herman and his Hermits are even more a raving success than they are here at home. Last year they came out top for the whole of the U.S., in a national popularity poll conducted by a trade paper. They even beat the Beatles and the Rolling Stones.     Herman and his group have earned eight Gold Discs for million sales in America, and sold nearly 15,000,000 records in all. It all began with Something Tells Me I'm Into Something Good two yers ago, and this has so far been Herman's only Number One disc in the charts at home. The others get into the top ten, of course, but in the U.S. they zoom to the absolute top, as Mrs. Brown, You've Got A Lovely Daughter did.     Herman found rather to his surprise that the Mrs. Brown disc was top of the charts in Japan too. "Japan is really just like those pictures you see of it," he says. "It's beautiful."     Herman's next big thrill is the release here of the film he made in Hollywood called "Hold On." Herman is the only pop star who has been signed for a major movie in Hollywood as an actor and not a pop star, but that is not really surprising, for Herman started out as a boy actor and not a singer.     He appeared for a while in TV's "Coronation Street" and one or two shows and TV plays. singing was part of his training as a young actor in Manchester, where he was born Peter Noone, 19 years ago.     He was a great frequenter of pop clubs and youth clubs and that is how he met his group and changed his life. (His name? It came from a cartoon series on TV called "The Bullwinkle Show" in which there was a character called Sherman who looked like Peter Noone. The group cut it to Herman and called themselves the Hermits!)