Did you see those prices Gaz? €65 for hub centric with the extended bolts. Cheapest by far. I couldn't get close to that. Gonna ring them for a postage quote.Yes I think you need to fill those arches a little more.
You want 5x120 pcd hub centric spacers. The width you need depends on your rim size, and how much you want to fill the arches.
On my 8.5x18 rims with et40 offset I needed 15mm spacers which brought them perfectly in line with the arches. Be interested to see what prices you come up with because I want to buy some more soon.