Selgas
On twin element water heaters especially those with twin thermostats a similar fault often occurs with the two thermostats are out of sinc with each other.
To test you have voltage ( the correct amount of volts and test the draw current in amps as well ), place the ends of a probe across one of the end terminals of each element and place the other end of the probe to a good earthing point, then test the remaining other element power feed the same way. If the meter shows that you have the correct voltage and current at the element that would indicate that the element is working properly. Do the same test for the other element as well.
Check and make sure that both thermostats are set to a suitable outlet water temperature and everything electrical should then be fine.
All of this is of course assuming that when you say you do not have any hot water that there is actually water running out of the hot tap/faucet. If there is no water at all then that my friend is a whole nuther story.
Hope all this helps. 
Selgas Services Ltd
Craftsman Gasfitters, Plumbers, Electrical Service Technicians
