i live in a ground floor massionette, i have a fairly new ideal icos boiler and a drayton digistat 2. the problem i have is that the only way i seem to be able to get hot water is if i turn the central heating on by the digistat.i don't have any other controls by the boiler to control the hw, just the digistat. can any1 help me as to why i don't seem to be able to get hot water without the heating on???