As I understand it, all we have to do is turn off the electicity
supply, and chisel out a hole in the wall for the box to fit into,
slot it in and hey presto. Is it really as easy as that?

Only you can know your own skill levels. The job consists of:

1. Turn off the electricity
2. Pull the MCB/fuse for the circuit.
3. Detach existing socket.
4. Drill/chisel out a chamber into the plaster/brick to the correct depth.
Use an SDS drill, if possible.
5. Drill hole and insert rawlplugs to attach backplate.
6. Punch out hole on metal backplate.
7. Insert rubber grommit into hole.
8. Thread cables through grommit.
9. Insert backplate into the chamber.
10. Screw backplate into rawlplugs.
11. Reattach live and neutral to socket.
12. Cut new piece of earth wire to size.
13. Thread earth sleeving over wire.
14. Reattach earth cables to socket, with one end of the new earth wire.
15. Attach other end of earth wire to the terminal in metal backplate.
16. Screw socket back into place.
17. Test the circuit, or get electrician/competent friend to test for you.
This requires specialist equipment, such as an insulation resistance tester
and an earth loop impedence tester. These are expensive and not the same as
a 5 quid "electrical tester" sold down the market.

If the socket has two earth terminals (i.e. you are using a new socket, as
old ones always have one terminal), attach one circuit earth cable into one
terminal and one into the other. The flying lead to the backplate can go to
either.

Christian.