Baxi hot water boiler working for the central heating but not heating the hot water.?

If you have separate (zone) valves for central and water heating, it could be the valve for water heating packed up, or blockage in pipes to hot water tank. The valve should have a manual by-p lever on it so you can open it manually. If this heats the water then faulty valve. If valve is open but not heating water then a blockage. All uming of course that timer is bringing on hot water.