Which part(s) of Europe? Mainland Europe is different again from the UK.
Essjay you need to understand how a GFI /RCD work and how a tank is grounded. Once you do you would realize the Differences between UK, Europe, Asia and north america don't really matter.
Lets start with the basic circuit breaker. Say you have a 10 amp circuit breaker on a wall outlet. When the aquarium pump is operating normally it is generally not going to need more than 1amp to operate. However if it shouts out it will pull more than 10 Amps of current and the circuit breaker will turn off the power. Note the circuit breaker is not there to protect you from Electrical shock. Its sol purpose is to prevent the home wiring from catching fire.
A CFC / RCD measures the current on the hot and neutral wires. If there is no ground fault the current on the hot wire will equal the current on the neutral. However when a ground fault occurs there will be more current hot wire and less on the neutral wire. The differences in current only needs to be about 0.01 amps or less for the GFI turn power off. If the current differences is only slightly exceeds 0.01 Amps a person could recieve a lethal shock. During a ground fault some of the current from the hot wire gets out of a wire flows through something such as you, tan then exits and flows into the ground through your feet. If doesn't mater if the GFI is grounded or not. And if doesn't matter if the aquarium pump plug has a ground pin or is double insulated.. The internal sensor circuitry doesn't need to be grounded to work. And the plug ground pin or double insulation doesn't mater to the operation of the GFI.
IF a pump fails such that the water of the tank becomes electrified , in most case the GFI and circuit breaker
will not trip. The tank walls and base are made of materials that do not conduct electricity. So the current flow though the water is zero and the GFI and circuit breakers will not trip. However if you then walk up the aquarium with no shoes on and the flour is a little wet you could receive a shock when current enters your hand and then leave through your feet. And only then will the GFI or RCD actually cut off power. They are designed to trip very fast to prevent any injury. In my own experience you may not feel the shock but you will hear a CFI or RCD trip.
Now if you tank the same tank and place a stainless steal wire into the water and connect the other end to a water pipe. Now the water in the tank is grounded. So if the pump fails and the water becomes electrified the GFI will immediately trip. likely before you put your hand in the water. So the safety designed into house wiring doesn't mater because the GFI is only looking at the current on the hot and neutral lines connect to the device you are handling or the device in your aquarium.
Although I did not look at aquarium hardware in the UK but with everythingI have seen on business trip in europe, UK, and Asia I have not seen anything indicating a signifiant significant differences in safety standards. The only difference in safety I have seen is the GFI or RCD's are relatively new and many older buildings don't have them or in some places building codes have not yet mandated GFI or RCD's.
