OK, I've heard back from them. I've specifically asked for W116, and even gave them a Wikipedia link to the model page to be certain they don't mistake it for a W123 (not so uncommon!).
They're asking 807EUR, taxes and shipping to Ireland included, for a full set of (in antracite, not green as queried...):
- front seats
- front armrest
- four headrests, removable
- rear bench
- rear armrest
Shipping is 15.97EUR, pre-tax cost is 678.15EUR, and VAT is 19% (which is wrong, as they should be charing 23% when selling to Ireland (i.e. the destination country rate))