Thanks Tony.
Just tried it. If I turn on the DHW for a very short while it will restart again but if i let it run for a few minutes till the water gets quite hot it wont restart. If i then turn on the CH and then turn on DHW it will supply DHW. Turn off the CH and DHW, then turn on the DHW...
My Vaillant Turbo max 282E combi (new 1997) will supply hot water when the boiler is cool/cold, but when I turn the hot water off and on again it wont start. It needs to cool down for a long time (hours) before it will supply hot water again, however when the hot water is on it will stay hot...