Ok nice one mate cheersFor the horn it doesn't matter which way round the 2 wires are connected, I think 1 colour matches on both Corsa's though and that was how I wired it.
The air bag although the Corsa D airbag has 2 plugs the Corsa C plug will only fit in 1 of the sockets on the Corsa D airbag and it will work just fine.
(I haven't tried to set it off to confirm this though 😂 ) No fault codes come up and it all behaves as it should on diagnostics though.