Place lamb chops in a single layer on a baking tray, scatter over thyme and garlic, season to taste, drizzle with olive oil and rub seasonings into both sides of chops. Cover, refrigerate to marinate (3 hours-overnight).
Preheat a barbecue or grill pan over medium-high heat. Add chops, cook to your liking, turning occasionally (4-5 minutes each side for medium-rare), set aside in a warm place to rest.
Bring a large saucepan of salted water to the boil over high heat, add spinach and cook until bright green (2 minutes), drain and cool under cold running water. Squeeze to remove excess water, place in a serving dish, season to taste, crumble over feta, drizzle generously with extra-virgin olive oil and serve with lemon wedges and lamb chops.