If you're lucky, all the components (boiler, pump, 3-port valve,
programmer
and stats) will all be connected together via a 10-way junction box rather
than having joints all over the place. Do you have such as box?

There is a double socket back box with a blanking plate containig a 10 way
terminal block strip with the cables running into it. Looks a bit of a
jungle (and fitting tight behind the plumbing) but is a start.


If so, have a look at http://www.sunvic.co.uk/ and navigate to Product
Installation Literature, and click on the first wiring diagram link. This
should show you what should be connected to what.

thanks for the link