Originally Posted by bobsadog
... trial and error route as I don't want to damage anything more.
Trial & error is not a smoke test...
Get yourself a test light and invoke your logical reasoning skills.
So you connect the large brown wire to one of the spades and turn the key in various positions until the switch supplies power where it should, changing the spade the large brown wire is connected to each time the results are not satisfactory.
In other words try different positions and eventually you'll find the correct spade for brown.
Then you'll know where the other wires connect.
For example key on power to IG (white) key turned to start power to starter (white with red) as noted above in reply post #2, and so on.
If the key has an auxiliary position hook up the spades accordingly.
It is not hard and this was my definition of trial & error.
I use a relay for the heater in order to take the load off the contacts in the IG switch.
You'll be proud of yourself when it works as designed.
You can do it!