Noise on start up

[Buzzard]

Hi, have a engine noise when I start my car, the longer it has stood the longer the noise. I want to change all the O rings, housing gaskets etc etc

would anyone please have a diagram so I can make sure I get them all, thank you

[Vauxhall Owners Club]

Are you sure it is not just hydraulic tappets that are starved of oil which is making a rattling sound?
Either way, the first thing I would do is an oil and filter change to eliminate oil related engine noises