Thank you all for your help. Managed to get a heating engineer to call today. He said it was the thermostat. Fitted a new one. Now have heat. Ah lovely. Warmer but poorer :)
Sorry Ollski - I appreciate your efforts.
Nothing is firing up the boiler now. Checked the fuse and that is fine. Turned off the electricity for 5 minutes as suggested. Nothing.
Usually the thermostat "clicks" in when turned up but that is dead also.
Did notice that when I turned...
My Baxi boiler has "gone out". There are no lights lit and there seems to be no pilot light lit. The boiler therefore is not firing up the heating system when I turn the Honeywell thermostat up.
My hot water is still hot. The appropriate lights on the timer in the airing cupboard are lit...