On Mon, 24 Aug 2015 05:50:31 -0700, JimK wrote:

A deep backbox behind the double switch with choc blok connectors doing
the job of the junction box. Mains in, 2 switched feeds out to the
lights...

Rather than a deep backbox, get a double backbox (not double size, but
one that takes two single plates). Drill a hole between the two halves
and put the choc blocks in one half with a blank plate on it. Less
squashed and easier to work with.

Here (on 'page' 53):

https://www.tlc-direct.co.uk/Technic...K/MK_BOXES.pdf