how can i fix my sime friendly e combi boiler?

my sime friendly e combi boiler will not give me any hot water. it will however, give me heating. I have noticed that the water pressure has risen slightly from the hot water supply, but it is always as cold as the cold water supply. When you turn on the hot water tap, the boiler doesn't fire up, so my guess is either a part problem or the microswitch isn't making contact. Can anyone be of further assistance, with a specific diagnosis and / or how to fix it as i am beginning to smell like wayne and waynetta slob