Heat the milk and 55 milliliters water together in a small saucepan till they are hot to the touch. Pour into a jug, stir in the sugar and dried yeast and leave it in a warm place for 10-15 minutes.
Sift the flour and salt into a mixing bowl, make a well in the center then, when the yeast mixture is frothy, pour it all in. Use a wooden spoon to work the flour into the liquid gradually and beat well at the end to make a perfectly smooth batter. Cover the bowl with a tea-towel and leave to stand in a warm place for about 45.
To cook the crumpets grease the insides of the cooking rings well, and grease the frying pan as well before placing it over a medium heat. Arrange the rings in the frying pan and, when the pan is hot, spoon 1 tablespoon of the crumpet batter into each ring. Let them cook for 4 or 5 minutes or until bubbles have burst on the surface.
Lift off the rings and turn the crumpets over. Cook the crumpets on the second side for about 1 minute only. Re-grease and reheat the rings and pan before cooking the next batch of crumpets.
Make the rarebit by melting the butter, adding the flour and cooking for a couple of minutes. Slowly add the Guinness to make a smooth sauce, then add the cheese, Worcestershire sauce & mustard. Mix well and leave it to cool a little then spread on the crumpets and grill for a couple of minutes.