Had a clear out and found some bits sitting around which I have no use for.
Head gasket £5
Head bolt set £5
Valve stem seals £5
Crank pulley bolt £1
All brand new, postage extra. Might save them a trip to the bin and someone else a couple of quid
Yes you have to make the hole, but it gets covered up again with the replacement panel.
I don't know the exact procedure for the astra, maybe it might be worth checking with someone who has a copy of TIS to know for sure
I changed the evaporator on my old vectra and there was no need to remove the dash. I removed the side of the centre console in the passenger footwell, and there was a cover that could be removed to allow access. You can buy a replacement cover that fits over the hole once you replace...