What cable for adding sockets please??

In the example above, one socket is a spur. It has been done using a junction box. Junction boxes must be accessible. It is more common for the spur to be taken from a socket on the ring, such that the socket then has 3 cables in it.

Every socket can feed one spur - so you CAN have as many spurs as sockets on the ring. But this is frowned upon, and it is better to extend the ring, so all sockets are on the ring.

In the example above, the socket that is a spur on its own, CANNOT feed any other sockets, since one piece of 2.5mm² cable is only good for 26 amps - which is what can potentially be drawn from a double socket.

Cookers MUST be on their own circuit, as must showers, immersion heaters, and any other large electrical loads.