Options for installing new power socket

Hi, I'd like some advice on the best way to install a new power socket. I need a ceiling mounted double socket in my living room. I initially thought I could run a spur from a socket in the bedroom above down through the ceiling but on closer examination of this aged terrace house's wiring it seems that both sockets in that room are already on spurs. God knows where they connect to the ring and I'm not keen on tearing up carpet and flooring to find out.
My initial thought was to install a FCU before the socket I planned on spurring from but I have no idea what runs before that. Other options were just to run a fused extension lead through the ceiling but that's a bit messy.
So, bearing in mind the current state of things and that "regs" are not going to be met without a full rewire, what is the best I can do to keep things safe?

using a FCU means the circuit can't be any less compliant than it already is or was when the wiring was installed.

If the existing circuit isn't RCD protected then use an RCD FCU to protect the new wiring and socket.

1. FCU before the sockets, this requires that the FCU is on the ring or is the first device from a junction on the ring, so essential to identify where the existing socket is connected.
2. Change protective device for the whole circuit to a 20A. May not be suitable if this circuit supplies high loads such as a kitchen
3. Convert ring into 2 radials of 20A each.

Identifying the wiring layout should not involve removing carpets or floors - with power off, sockets can be removed to see how many cables are behind, and basic continuity tests will identify which cables go where.

Thanks for the prompt replies. Each of the two sockets in the room only have one set of wires connecting to them so neither is on the ring, nor are they daisy chained. I would therefore expect them both to be separate spurs.

Firstly are you sure it is a ring final circuit (RFC) or could it possibly radial?
For multi spurred sockets on a RFC, you will require to fuse down at the intersection of the ring prior to any spurred socket outlets.
As previously mentioned there is now a requirement for newly buried cable in walls and any new socket outlets to have RCD protection, do you already have this protection on this circuit? If not you need to provide it either at the board or at least before any new work.
If you can spur from the full circuit and this then means breaking in to the cable rather than an existing socket outlet, then you will also require to comply to the regulations concerning accessible or maintenance free joints.

Unfortunately if you do not have any testing equipment, that is suitable to confirm the configuration of the circuit and also confirm the work you intend to carry out and prove safe, you are going to struggle complying to the requirements of BS7671 and Building Regulation part p.

Even as electricians it is hard to be 100% sure that there is not a spur from a spur. But using low ohm meters and loop impedance meters one can identify most of them.

What one needs to do is assess the risk. As already said using a FCU instead of a socket limits to supply to that socket to 13A however where multi sockets are fed from a FCU then it becomes far more likely that it is 13A rather than some thing below that level.

My mother has only a kettle which plugs in and uses 13A so for her every socket could be spurs from spurs and it would be unlikely to exceed the maximum loading for the cable. Which means the MCB could be changed for 20 amp and it would not cause a problem.

This is the easy way out, if 20A is enough then swap the MCB.

But you need some level of skill and to be safe if you don't have the skill easy way is to get some one who does.