Andy
Just go to somewhere like Dick Smiths / Tandy etc., and buy a small project box (size to suit)
Sealed Polycarbonate Box (H2864) - Dick Smith Electronics - Australia.
and also get a plastic connector strip/terminal block (normally 12 connectors to a strip)
12-Pole Terminal Block (P4848) - Dick Smith Electronics - Australia.
Make all your terminations/connections in the box - then run simple wiring/multicore to the socket
PS After you have made all your connections - fill the box with melted candle wax - that will keep it sealed and water tight