Many thanks, Colin. Cognac is lovely and only 30 minutes from us - a stress free half hour on French roads!
The VIN issue is odd. We have the habitation door plate but it only has the serial number of the van, not the VIN. There's another plate inside the door, low down, with an Aufbau Nr. We also have plates on the drawbar by the hitch and one on the axle - both of these are AL-KO plates (they made the chassis, I believe) and don't appear to have the VIN on them. I've attached photos of all 4 plates in case you're interested!
I've had an email exchange with Eriba Loisirs in Cernay having been referred to them by Eriba HQ in Bad Waldsee. They have said that none of the numbers I've given them help and that they can not provide me with any more information... I've also emailed AL-KO to see if they have any more information but they haven't got back to me yet.
Next step, assuming that I cannot find the VIN anywhere, is to go down the FFVE route but I still need the VIN to get that ball rolling...
Heigh ho!