potterton performa 28i C/H but no hot water?

Hi my potterton performa 28i started playing up yeaterday we had no hot water or heating. The plumber called round and said it needed a new pump.........central heating worked but still no hot water. Then he said it needed a new board...still no hot water, so far this has cost £430 and we still dont have any hot water! Any ideas gratefully appreciated. Oh the sensor light is on now!