Hi Matt,
out of idle curiosity, was it a garage which had plenty of experience with A series Citroens?
I assume that you made them aware of what you planned to do with the van, so any 2CV-based business should have made sure that the chassis was in tip-top condition.
If they didn't, that's more than a little disappointing.

Some other observations; one of your photographs shows a radiator cap fitted to the fuel tank filler, instead of the proper (vented) item. If that was used on the trip, it may well have restricted fuel flow to the engine, causing it to run lean and overheat.

Also, the starting problems you experienced were almost certainly down to a 'below-par' ignition coil, which is why a new coil, and maybe a spare, should have been on the shopping list when preparing the van.

In case you're wondering, I do have a bit of previous experience with this sort of venture, having prepared a (blue) Acadiane which drove overland from Australia to the UK in 1996/97...