Alan Dempster wrote:

I like it - still not stricltly 'cosher' because there's two spurs
effectively from the same original DSO, but at least the cable is protected
to being used within its load limit.

It's 100% kosher. Nothing in the rules for spurs (Appendix 8 of the IEE
On-Site Guide) forbids two separate spurs being connected to the ring at
the same point.

There is an overriding consideration though, in the form of Reg.
433-02-04 of BS 7671 itself, which includes the words:

" [...] Such ring final circuits are deemed to meet the requirements of
Regulation 433-02-01 if the current-carrying capacity (Iz) of the cable
is not less than 20 A, and if, under_the_intended_conditions_of_use, the
load current _in_any_part_of_the_ring_ is unlikely to exceed for long
periods the current-carrying capacity (Iz) of the cable." [My emphasis,
and note that Iz is the _as_installed_ cable rating.]

Now to struggle with four lots of 2.5mm sq. conductors in the one socket.
Deep joy (in a deep box!!!)

That should not be a problem with double-gang sockets of reputable origin.

--
Andy