For burnt-down buildings, I believe a fire arson or flying jets crashing into buildings (just like the World Trade Centre) would stand a higher chance of getting the whole building on fire.

In summary, the message I am conveying here is it's not that difficult to find a competent electrician. Of course, one can choose not to trust the electrician since you wont' know his background (unless you scrutinize his credentials for certification) but in reality, most experienced or competent electricians would do fine. Otherwise, we would hear buildings being burnt down in the news every day of the week due to poorly installed water heaters.

But for me, it is useless as the storage heater will be hide inside ceiling. If many people using, you have to set it max to reduce the hot water usage ratio.

The only point worry is, how long the heating element can last. And what is the cost to replace. This might turn you off.

Imagine have a tong gas size at the corner of the bathroom.    That is the 40-50L size of a storage heater. With the piping and wiring, it is an eye sore in your bathroom. If with a small bathroom, it look crush in there.

Storage heater have to install height above. Who want to climb ladder adjust the knob everytime ? It is not same as instant heater height level. You going to knock your head with that tong gas size heater in the bathroom.   

You can mix the water at the tap to get the right temperature you want. It is not same function as instant heater. There is no logic to adjust the temp...before use ?   

It is not necessary to install a pressure gauge for the incoming water. I believe the tank can stand well above the normal house water pressure.

The pressure relieve valve don't have the gauge reading. It is just a spring load valve mechanism. You can test it once a yrs by pulling the shaft ring. So not necessary to be eye visible the storage heater. There is nothing to see at all.