LEAD: PLAYERS By Jilly Cooper. 465 pp. New York: Ballantine Books. Paper, $8.95.

PLAYERS By Jilly Cooper. 465 pp. New York: Ballantine Books. Paper, $8.95.

As a television critic, I often must suffer the pity of snobs - of people who insist that when it comes to television, British is better. I say they're wrong. ''The Singing Detective'' proves me right. So does ''Benny Hill.'' And so does this British novel about British television by a British writer and television personality, Jilly Cooper.

If we are to believe ''Players,'' then at least the book does try to explain why British television produces so much overrated twaddle. In this novel all the producers, directors, owners, regulators and stars of the English airwaves are oversexed, overdressed twits and idiots. But we should not believe ''Players,'' for it is only trash, bad trash - worse than anything America puts out (that is, worse than the published trash atop our best-seller lists or the televised trash at the bottom of our ratings).

''Players'' is supposed to be about a fight to win a regional television franchise, fought among the sort of characters who happen to run into one another on the Concorde. Yet the book is filled not so much with plot but with parties. At these horrid affairs, men with strange names, like Fred-Fred, wear stranger silk shirts - pale pink and blue, for instance - while women think dumb thoughts - ''Oh God, sighed Lizzie to herself. I daren't ask what electronics are'' - and men speak their dumb thoughts: ''You must feel like Sisyphus,'' one man says, and the other replies, ''I don't know who he is, but I'm sure I do.''

Trash must have its sex scenes. Some of the examples in ''Players'' are offensive not for their sex but for their violence and silliness. A woman who is beaten by a jealous boss and lover stoops so low as to justify the attack on herself: ''He had provocation.'' But most of the book's sex is simply ridiculous. A sampling: ''. . . said Maud, noticing his long fingers and wishing they were unbuttoning her silk dress.'' '' 'When am I going to see you?' gasped Sarah, as Rupert's other hand slid down underneath her panties at the back.'' ''The whole building thrummed with lust.'' ''She looked desirable even with croissant crumbs on her lips.''

But the sex is no more ludicrous than the characters performing it. Certain American network bosses like to buy and produce shows that can be described in just one sentence. That is precisely how the author describes her characters, like so many ''high-concept'' movies of the week: ''Troublesome, short-tempered, but monumentally talented, Declan O'Hara was the B.B.C.'s hottest property.'' ''Rupert was like a sleek capricious thoroughbred, rippling with muscle and breeding, about to win the Derby.'' And Basil ''runs a phenomenally successful wine bar, dabbles in real estate, hunts four days a week in winter, plays polo all summer'' and has sex with the prettiest girls ''in four counties.''

But at least these Brits do say the sorts of things we expect Brits to say: ''You are smashing.'' ''I'd love a piece of that gateau, and those bramble preserves look quite delicious.'' ''That fish pate's champion.'' ''Utterly bloody Mummy's put Rupert Campbell-Black next to her.'' ''You really ought to eat some of this shepherd's pie. It's frightfully good.'' ''Why the hell can't you find a girl of your own class?'' As a typical Brit might say, in sum: What bloody rot. But I don't mean to use this bad book as an excuse for some rabid Anglophobia. You see, I used to be an avid Anglophile - until I became a television (and occasional book) critic and was subjected to just such Brittwittery as this. But I know that it is unfair of me to dismiss Britain only because Britain produces (and we import) some unbearably boorish shows and books - just as it is unfair of our own snobs to dismiss American television only because it is American.