Thanks everyone for your input. I’ve spent a bit of time looking at the manufacturer’s site and retail sites for this piece. I am of the opinion it is a metal construction clad in timber as they offer a walnut or wenge ‘finish’. I’ve put a price in to the guy with a ‘region’ big enough to get a metal substructure fabricated if needs be, stating that due to the unusual design, I can’t work out an exact figure as I don’t know exactly how long it will take to do, and pointing out that the unusual joinery will need a prototype making first to check for weight bearing.
That’s about all I can do. If he balks at the estimate, well that’s down to him. If he wants it done dirt cheap and is willing to take a chance on it collapsing on his dinner guests, he can get someone else to do it. Or he could buy one in a shop in England and get it transported over for about €7,000.

Doing the best I can with what I've got