When Stephanie Beacham arrived in Hollywood four years ago for her first U.S. television series - a Dynasty spin-off called The Colbys - she was coddled and spoiled by the glamour-oriented Aaron Spelling organization. As Sable Colby, the scheming, seductive wife of Charlton Heston, the British actress had an amazing, old-fashioned "Hollywood experience," she recalls.

"If a hair was out of place on a Spelling show," said Stephanie, "there would be memos shooting all the way down. There was one scarf that I wore as Sable, and Aaron phoned up Nolan Miller (the Dynasty fashion designer) and said, 'Stephanie Beacham in the rushes today looks like the road show of Carmen Miranda.' When you have people so onto things, you can relax."

But now Beacham is on her own. Pretty much, anyway. Jumping into the rough-and-tumble world of network sitcoms, she has made the eye-opening transition from Sable Colby to a no-nonsense nun who is unwillingly put in charge of a group of unruly orphans in the new NBC series Sister Kate.

Madison Avenue thinks Sister Kate has a pretty good shot, even though series with religious principles usually flop and even though Beacham will face the formidable competition of CBS's Murder, She Wrote when the sitcom settles into its regular season Sunday slot.

Beacham also has to cope with the hurdle that TV stars with British accents have. This is a belief that such accents are not readily accepted by grass roots viewers in weekly series. Beacham thinks Joan Collins may well have shattered the accent-taboo once and for all in Dynasty.

What Collins was to Dynasty, Beacham was to its spin-off, The Colbys - a nasty but gorgeous attention-getter. "I think I have a lot to be grateful for as far as Joan is concerned," says Beacham, agreeing that Collins opened the door for her. That's why they thought in terms of looking for a Brit for Sable.

Joan Collins proved that middle America can accept a British accent. "It was her voice," says Beacham. "I think people suddenly realized it was comprehensible. Something to do with diction. Something to do with articulation. It's all Joan that did it. God bless her."

The question now is whether Beacham will get the audience's blessing in Sister Kate, in which she out-toughs the collection of kids put in her charge at Redemption House, a Catholic residence for children. And Beacham, a 40-ish beauty with a mind of her own, is clearly taking steps to ensure success now that she no longer has the security blanket of the Dynasty team to protect her.

Beacham is ensuring that the nun she plays is attractive: "I learned from Aaron Spelling, playing a vain woman, just how I should be photographed," she said. "If you're playing a woman in a prison camp and you're worried about camera angles, you're dead. But because Kate is quite harsh, unless she's pretty, she's going to be unsympathetic. The audience has got to love her."

"On Sister Kate," she says, "I push to know what are the parameters of character, what are the parameters of dress. And I don't get much solidity. I am feeling very insecure. A few things are coming from the network, but I haven't yet put a face to where the notes are coming from.

"It's not knocking what's happening here. I just know that I've had an amazing, old-fashioned Hollywood experience that I am really grateful for with Aaron. The other side of that is, how can anybody not be completely thrilled, having been on film playing a bitch, to then be allowed out in front of a live audience in a sitcom as a nun?"

Divine Inspiration

Beacham is aware that series about the clergy are usually long shots, although the fantasy The Flying Nun, with Sally Field, was an exception. In any case, she wants a full-time adviser for the irreverent Sister Kate from the Los Angeles diocese. And she says she's contacted nuns fore their views about her portrayal.

"I search them out myself," she says. "These are very straightforward ladies. A couple of them came to the pilot when we recorded it. I must admit their only comment was that it was very funny. But there are things that are definitely inaccurate. I jump in and out of the habit rather alarmingly. It's not actually what they do."

She wants the full-time adviser "so we don't get a lot of hollers and screams. And anyway, there is no comedy without truth. I don't want to be a woman in a habit. I think the fun will be that she is genuinely a nun."

Beacham may have enjoyed the pampering while playing Sable - "It was the studio system. It's Cinderella" - but she makes perfectly clear that she is capable of taking her life into her own hands. She says, for instance, that she has no manager.

"Nobody manages me. I manage to swallow the fact that you have to have an agent. I will never swallow the fact that people have money managers. I have an accountant. I do my own checks. If I fail financially, I'll have done it all by myself.

Beacham is not unaware of the situation's ironies, however. "From a glamorous bitch to the vows of chastity, poverty and obedience. I do a big curtsy to NBC for having the vision to see that I'm capable of it.