HERMAN'S HERMITS currently filming "Mrs. Brown, You've Got A Lovely Daughter" at Shepperton, fly to America next month for a marathon two-month tour of one-nighters.     The tour, which starts on July 13 in Alberta, Canada, takes the group through Seattle, Vancouver, Dallas, Miami, Chicago, Toronto, Washington and other major cities, ending in Honolulu, Hawaii on September 9.     The group makes no appearances in Britain before the tour, as filming commitments do not finish until the day before they fly out.     A new sngle from Herman, probably two songs from the film, will be released before his return.