>...unless you are going to do major changes to the wiring. (I don't know where the line is drawn really.)
By us it's the same law, but I would consider this a major change.
>Why are there two types?
Half recessed for places where you don't have enough space behind the socket e.g. to make more connections behind a socket.
>Does the ground pin protrude beyond the socket in the half recessed version?
Yes, but it has a "ring" which protrudes around the plug to protect the pin.
