No hot water

If the shower isabsolutely cold then I think you may have a faulty Thermal Cut Out

A faulty TCO will have no continuity across the twoterminals (The black thing on top of the heating tank)

Therefore a good TCO will have power at bothconnections and a faulty TCO will have power at only one.

(The function of the TCO is, if the water over heatsit cuts the power off to the elements)

See Video.

http://www.youtube.com/user/showerdoc#p/u/2/_zi8JbEMYMs

Ifthere is some heat it may be a faulty element in the heating tank (there aretwo, three in most 10kw showers) you can check them with a multi meter youshould have a reading of around 12>18 ohms.

If you have power to theelements and no heat it's probably the elements, no power to theelements then it's probably a micro switch.

If you don’t have amultimeter  we sell them at £10 each with a guide on how to use them forchecking and testing the various parts of your shower.

Apart from helping to fix yourshower, they are really useful for checking you have a power supply toappliances, for checking fuses, letting you know much power you have left inbatteries

(so you know if they are dud ornot)  and lots of other jobs, in short they are well  worth the £10.

http://www.showerdoc.com/installation/electrical-products/SKYTRO-600-005-Digital-Multi-Tester

I am not sure exactly what the question about the multimeter is, however it is an essential bit of kit for testing any appliance.