AN extensive overseas itinerary has now been completed for Herman's Hermits, which will keep them away from Britain for the whole of the summer. The schedule includes engagements in the Phillipines, Australia, Mexico and the United States. Also set for the group are three major TV appearances and two Scottish dates.     The Hermits fly to Manilla in the Phillipines for two days of concerts on June 14-15, and three days later they begin their three-week season at Sydney's famed Chequers Restaurant. The group then travels to Mexico City for a nine-day cabaret stint at the Caminoreal Hotel.     There follows a lengthy schedule of concerts, night clubs and state fairs - including Las Vegas cabare - in America,

taking the group up to mid-September. These engagements are currently being finalised by the CMA agency in New York.     TV dates in Britain for Herman and the group include ATV's "The Real Mike Yarwood" (next Monday, 7); a return appearance in ATV's "This is Tom Jones" (May 2 in London, May 4 elsewhere); and BBC-1's "Basil Brush Show" (Friday, May 2). Following their previously-reported concert tour with the Love Affair, they also play Scottish one-nighters in Ayr (April 25) and Kirkaldy (26)     Herman is to be featured in an ITV advertising campaign for a well-known cosmetics firm next month. He filmed a series of commercials for a hairspray in Venice in February.