LONDON — Holidays traditionally are the time when the British TV industry pumps up its programming schedule. And with the coming launch Sunday of the terrestrial Channel 5, the four-day Easter weekend will be the most competitive ever.The U.K.’s established terrestrials — BBC1, BBC2, ITV and Channel 4 — are pulling out the stops with new shows, specials and Hollywood blockbusters. ITV, despite continuing to downplay C5′s chances, not only is upping its programming, but also directly targeting the C5 lineup — tacit admission that the new kid on the block is being taken quite seriously. Expect the worst C5′s debut is likely to be a glitch-ridden affair, and at first glance its programming leaves a lot to be desired. But that also was true of Channel 4 when it launched in 1982, and it became a success. C5′s launch may prove disastrous, but the competition is keen to keep C5 at bay for as long as possible. As the most mainstream of the terrestrials, the ITV network is perceived by many observers as having the most to lose. C5 head of programming Dawn Airey refers to C5′s programming, style and look as “modern mainstream.” Essentially, that means it is intended to appeal to younger mainstream viewers, a big part of ITV’s demographic. Media analysts estimate that C5 will grab a 3.5% to 6% share of the terrestrial TV advertising market by the end of its first year. Some say C5′s first-year ad revenue could top $150 million. It is thought C5 will turn a profit in 2000. Neil Blackley, an analyst with Merrill Lynch, said that if C5 “is successful in hitting the 14-to-35-year-olds, they could become the Pro Sieben or M6 of the U.K.,” referring to the German and French channels that have small ratings but do well in advertising. C5 is hoping to reach a 5% audience share come next year. Its first on-air ad is skedded to be for fragrance Chanel No. 5. C5 launches late in the weekend: 6 p.m. Sunday, which according to C5 head of corporate and public relations Sally Osman, is “the ideal time, because people are returning from their holidays.” The schedule is not particularly front-loaded, reflecting both the fact that C5 is stripped in the U.S. TV style, and therefore is looking to build viewer loyalty for its shows over time, and also within budget limitations. C5′s programming budget is a mere $174 million for its first year, whereas ITV commands more than $1 billion annually. C5′s big drawing card is supposed to be movies, airing every weekday night at 9, which is the official U.K. watershed for programming geared toward adults, and afternoons at 3:30. Advantageous angle But although ITV has far deeper pockets than C5 for acquiring product, C5′s advantage is that its movies can run uninterrupted, whereas ITV, as is stipulated in its broadcasting license, has to break for its nightly newscast at 10. C5 is leading on Sunday with a taste of what it has to offer, such as Britain’s first daily soap, “Family Affairs,” some news briefs to get across what its 8:30 p.m. newscasts will be like, and an introductory look at its David Letterman clone, “The Jack Docherty Show,” the first nightly chatshow in the U.K. The biggest first-night show is the one-off drama “Beyond Fear,” based on the true story of a kidnapped female real estate agent. The other channels have major movies that evening. On ITV is “Sister Act 2: Back in the Habit,” the BBC has “Born on the Fourth of July” and Channel 4 has “Glory.” Later in the week, ITV is airing a special one-hour episode of the soap “Emmerdale,” and debuting Granada Television’s new period drama “The Grand” — billed as a raunchy “Upstairs Downstairs.” Big pix plot Movies figure large in the C5 universe, but it also is hoping to make inroads in the timeslots it perceives the other channels are underexploiting — afternoons and latenights. To that end, it has “The Bold and the Beautiful” at noon weekdays, repeats of “Family Affairs” at 12:30 p.m. (first run is at 6:30 p.m.) and “Sunset Beach” at 1:05 p.m. “5′s Company” — which Airey describes as akin to a “radio phone-in show on television” — follows at 2 p.m. and leads into a movie. Latenights begin at 11 p.m. with “The Jack Docherty Show,” followed by standup comedy, news and sports, largely targeting male viewers. There will also be soft-core sex films on weekends.