You can join them. Neatest solution is a dedicated enclosure with say DIN
rail terminals. However junction boxes are fine if you are not planning on
plastering over them. There are also plenty of other enclosures you can
use with wago terminals or crimps etc.


Having just "done" my first wagobox (2 way light circuit with incoming power
and the light at the same end, so four cables into the box), I must say I am
very impressed with them. They do a nice mini-pack with four boxes and an
assortment of connections which is a handy and reasonably priced "taster".
For the case described, you could use a pair of 773-173's to take the two
ends of each ring main (2.5 solid) and connect to 6 mm^2 "conduit" wire to
go into the CU, making a relatively neat and un-cluttered layout. Easier to
to than crimping, if tails are short or space is otherwise tight.

Agreed, the DIN rail is neat and looks very professional: might be the
option if you wanted to tidy up an old installation prior to selling, but
it's not cheap.