THE SIGN GREETING visitors to the City of Stratford emphasizes the dual forces of city and country life. This, it proclaims, is the home of the Stratford Shakespeare Festival and the Ontario Pork Congress. Similarly, Lucy Peacock and her husband, Christopher Thomas, have created a balance between her career as a leading actor at Stratford and their family life in the country, where he raises thoroughbreds for the international racing circuit. The half-hour drive between their 100-acre property and the theatre is Peacock's transition time. "I change hats in the car," she says, "from the farm hat to the actor hat. I do vocal warm-ups, too." The drive home is equally useful. "I'm pretty pumped up after shows and it takes me awhile to come down." At home, Peacock gets out of the spotlight and gives her many stage personae a rest. She reads, experiments with new recipes, and putters in the garden. For the holiday season, she decks out the house with wreaths and garlands made from the cedar hedges they planted on the property. A pond is among their landscaping plans. They have the spot picked out, near an antique bench Thomas purchased at an auction. "We keep giving each other ponds and water features for special occasions," she says with a grin, "but we never get around to actually digging the hole."