LONDON, Jan 23 (Reuters) - Britain's national health costs watchdog has recommended Bristol-Myers Squibb and Pfizer's anti-clotting pill Eliquis for preventing strokes in patients with an irregular heartbeat condition called atrial fibrillation (AF) The draft guidance from the National Institute for Health and Clinical Excellence (NICE) opens up a potential new market for Eliquis, which belongs to a new class of medicines designed to replace the decades-old blood thinner warfarin.