OP
ben5010
Not in so many words. The wiring regs (BS7671) runs to over 400 pages. However, in most domestic installations, new cables in the wall and new sockets will both require RCD protection. Often the best way to achieve this is to add an RCD to the whole of the existing circuit. Even better may be to install a new consumer unit with RCD protection to all the circuits.
As far as the requirement for a new ring is concerned, it depends on what loads may be connected to the existing ring and what loads are proposed for the new sockets. Its possible to run a whole house on one socket ring circuit. On the other hand, you wouldn't want to find the the circuit breaker or fuse kept tripping due to overloading of the circuit.
Just out of interest, how much had they quoted for the job and how many quotes did you get?
They had quoted me £147 with me to supply them the 5 sockets