No hot water heat only boiler

It sounds like you have a heat only boiler, which means you will have tanks in the loft and cylinder to store hot water usually in an airing cupboard.

Make sure that your programmer on the wall is set for the hot water to come on. If it's in a timer mode it would be best to set it to be on constant just so you can test it. Turn the heating off. Go to your boiler and check to make sure it stays on. 

Here is an example image of a common programmer that you might find in your home. You can also search for your specific central heating programmer or room thermostat user guide using this link.