How's this:
http://www.tlc-direct.co.uk/Main_Ind...Index/Joints_R
esin_Filled/index.html
FWIW, if the question is electrical bits, the answer is usually TLC :-)

btw, just noticed:
"The straight through kits do not include connectors, order Through Crimps
or Butt connectors to suit the size of cable being joined"
--
fred

thanks ! looks interesting...