Central Heating won't stop and there is no hot water?

My problem has switched since I repressured my Vaillant Turbomax 824 boiler. The central heating was not working and the pressure was at 0.8. I followed instructions to repressurise and slightly overfilled (2.5). For most of the evening I had heating and hot water. Then I noticed the heating had remained on, even though the timer should have turned it off. In addition, I can no longer get hot water -- if I turn the boiler on, regardless of setting, temperature etc, the central heating goes on full blast and no hot water is produced.