New to fibre broadband

[#1]

To check the wire pairs you only need an ohmmeter or multimeter.
As long as each pair is isolated from the other wires they just need to twisted together. Then an ohmmeter applied across the other end of the wires to determine which pair is which.
For example if only the extension in the bedroom is required, disconnect the pair from socket and twist together.
Back at the master socket putting the probes across the 2 same coloured wires will determine which ones are correct when the multimeter registers continuity.

[#2]

Thanks - thought there would be something to do the job.

So, with the right tools, it would be a straightforward quick job to sort the wiring out. Simply disconnect all wires on the face plate downstairs, twist one pair together then go upstairs and disconnect all wires in the desired socket. A simply test would then indicate which is the "live" pair which could then be connected both up and downstairs and hopefully Bob's your uncle.

It's simple because no other extensions are required - a problem for the future if they ever are needed!!!

I would still suggest replacing the master socket face plate with a filtered version like the one I previously mentioned - if nothing else it's tidier than using a micro filter.

Brian