ACEA is a manufacturers association, not a law. What is the law referred to in your first post? Are Swift a member of ACEA? Or is the base vehicle manufacturer responsible for the problem part.
Apologies, wrong choice of words, "Code of practise", but bottomline Swift are selling caravans/motorhome that within the warranty period are unsable.
They are not providing spare parts, in what I would consider a resonable timeframe.
If your you car was off the road with a faulty alternator and the dealer said "Ford" don't make that part it will be a month from the actual supplier!! Is that acceptable to you??
Scale of manufacture is irrelevant Swift sell them they should ensure prompt aftersale repairs.
Swift claim to be the leading manufacturer, making them is only the start of their responsibility.
If they can't keep those they have already sold on the road they should stop selling more.