2.5mm cable for extra sockets

[JohnW2]

All the rings (and yes they were rings) in my parents house were on 15A rewirable fuses for over a decade, they rewired the place when they moved in but did not replace the fusebox at the time.

Fair enough, but the primary reason for the existence of (UK) ring final circuits is that it allows a cable with a CCC of 20A to be protected by a 30/32A OPD. If that OPD is 20A or less, then there's really no point in having a ring (other than, perhaps, EFLI or VD considerations for very long circuits).

More recently I've also seen youtube electrians reduce circuits to 20A as a quick fix when broken rings or chains of spurs off spurs are discovered.

Yes, that is done. However, in the first case that's because the ring has 'turned itself' into two radials (well, two branches of one radial). In the second case, That really is (or should be!) just a temporary 'workaround' until the issue can be addressed properly.

Kind Regards, John