From your answers you are clearly not competent although competent has now been dropped as a measure of skill, it was the name given to those better than skilled, 2.5 mm² cable does not have one fixed current rating it depends on how installed and if thermoplastic or thermosetting cable, however it is unlikely to be rated at 32A in the main we consider it as rated as 22A unless we have installed it so know exactly the route or there is an installation certificate.
We are permitted to protect if no branch from the cable and it is unlikely to get damaged and within 3 meter of origin at the detestation of a cable. So it would be permissible to take a 2.5 mm² from a 32A MCB to a single socket, but not to extend from that socket, as the 13A fuse in the plug or two 13A fuses if a double socket is considered as protection from overload and this is what happens with any unfused spur. But that is the only time we are allowed to supply a socket with more than the cable can carry and then the loop impedance of the supply must be low enough so with a direct short the supply overload will disconnect within 0.1 seconds, so loop impedance must be better than 1.44Ω. Today that figure is reduced by 10% which means the cheap Martindale EZ150 tester which passes at 1.5Ω is not good enough so needs a meter costing not £40 but £200 to test the socket is within the regulations.
Without test gear you must play safe, so the best option is when extending to use a fused connection unit (FCU) so fused to 13A total as then the cheap £40 EZ150 tester will give you a usable result.
In your case replacing the first junction box for a FCU would then allow you to fit as many sockets as you want, or replacing the MCB for a 20A version would also allow you to extend with 2.5 mm² cable.
Although you could wire with 6 mm² cable only some sockets will take two 6 mm² cables and there is no way you could spur off as simply not enough room in the terminals of the sockets.
Judging from your answers and your inability to read and comprehend the answers already given, I would say get an electrician to check over whole installation and modify as required to make safe, if one circuit is so wrong this must ring alarm bells and one must question what other errors there are with the wiring.
As said it would seem some one has fitted a socket to old shower or cooker supply, and if the cable used was less than 3 meters long that would have been permitted, but then some one has added more and more which clearly is not permitted. This is unfortunately what happens when people do not stop and fill in the minor works or installation certificates, when one fills in the paperwork even if put in the bin after the testing required high lights errors, failure to inspect and test means errors go unnoticed, and it can go unnoticed for years and years, until some one uses high current devices in those sockets. Fact that a socket works is not enough.
