Seven years is way too long for a timing belt, so yesterday we took the van to a Fiat dealer on the mainland.
They called 5 hours later and told us this was going to be time consuming and expensive because several bolts were seized to the point where more force would cause them to snap off.
With penetrating oil and a heat gun they will try to keep damage to a minimum, but it may take a few days(!). They gave us a brand new Nissan Note so we could return home and wait for their call.

Actually it took 3 days to replace the timing belt.
A long, long list of parts that were replaced because undamaged removal was not possible, including the pricy water pump. The total bill: 785 EUR, the irony: the old belt showed not a single crack and might have lived another 7 years......