My baxi boiler has stopped working...help!!?

If it is not a combi boiler, and your pump is running okay, then you have 2 motorised valves near your hot water tank. One valve is for hot water, and the other one is for heating. The valve for one of them is stuck in the closed position. You can check which one by putting your hands on both sides of the valve and you will find that one side is hotter than the other side. This will be the faulty one. You can open the valve manually, by moving a slide on the side of the valve and push it into a notch. Then try your boiler again.Another possible fault is that the water tank that fills your hot tank has run dry. This is probably due to a fault with the ball valve. It can have tiny bits of grit stopping the water re filling the tank. You need to try to clean it or replace it. Good luck.