Have a look at the coolant cap seal (WHEN COLD!!) :LOL: and see if it's split. The Insignias' are notorious for it (and all Vauxhalls of that sort of era, my 2007 Corsa had the same issue). If it isn't that, then check the Coolant reservoir itself for any obvious splits (whilst cold but also try...
Halfords Anti Rust primer (y)
I can couch for as I have done bits on my 2007 Corsa with it, and fingers crossed it hasn't come back :oops:
I am gonna do my steelies too, although I have some fancy aftermarket trims on them at the moment so might just forget about it :ROFLMAO:
If you mess with anything like rod ends or suspension (or anything really apart from brake stuff) it will throw your alignment out.
Sounds like you've maybe done something incorrect in your previous endeavors. We all learn somehow mate, I have made countless embarrassing errors in my years of...