Ok guys, gathering your precious info, I end up with this. Please correct me if I'm misunderstanding:
Locally behind the glovebox only:
1] Green line 1: from switch to the vac "element" (which is close to the ac recirc valve and which comes back with spring force)
2] Green line 2: from switch to the reservoir tank
From under the hood:
3] Grey line: intake manifold > under the battery > grommet > reservoir tank
4] Lilac line: headlights > below the battery > grommet > headlight adjuster
@slkbagnolet have a look at this post
Vacuum headlight adjuster So, to the best of my recollection, the connection from the manifold is a grey pipe which heads across to below the battery and through the multiport grommet to the adjuster - and from the adjuster the purple pipe comes back through the grommet below the battery to connect to the headlights. It's important to connect them the right way round to the adjuster. They are quite brittle and I used small silicone tube extensions, cut from a roll I had lying around, to make the connections easier after trimming the ends of the existing pipes.
Is the adjuster = vacuum reservoir/tank?
Don't hesitate to comment!