To enable the intermittent wiper feature on the Vectra stalk (Mutliplug L23/24/27 on the dash’ loom), is a simple matter of just connecting the relevant stalk wires to an additional  relay, and moving and putting in a couple of other wires…

...Not quite! As it took an absolute age to get my head around what going on.

Here’s the connectivity of what I’m doing… 

And how I did it…

With the new [additional relay], gnd, and wire (J (pink))