This forum was a great source of info, so thought I'd give a bit back. I recently bought a new 2019 9,500 mile Citigo 3rd SE for my daughters to learn in. Learned from this forum that they have a propensity to rusting around the rear wheel arch liners so though I'd pay it forward and give my experience. I bought two rear arch liners from buycarparts.co.uk - they are a clone site of AutoDoc - it's AutoDoc that fulfills the order, but they are a few quid cheaper than the AutoDoc site. £43 for both including delivery. The item numbers from buycarparts are 6601-01-9516831P and 6601-01-9516832P. Delivery takes around a week. I bought a pack of self-tapping trim screws from Halfords but only actually used two of the screws. I also bought a can of Dinitrol sealer. Fitting was a doddle. I hosed the arches - having only 9,500 miles on the clock meant there wasn't much road dirt under there. I inspected the fuel tank neck from behind the swing and the original paint appeared to be all intact and clear with no sign of corrosion. I then sprayed Dinitrol all over - it's a messy job if you want to get the can up above the filler neck - but worth it. Then took the wheels off. The liners are a bit rigid in this cold weather, but go into place easy enough and clipped into place pretty securely. They kind of find their place and feel pretty solid with no fixings as they are moulded around the arch profile including the factory bolt that sticks out - but wanting a bit of belt & braces I drilled a small hole on the inner surface for a self tapper, removed the arches and sprayed copious amounts of Dinitrol into the hole to protect the drilled metalwork. Then refitted the arches, screwed the self-tapper in and then sprayed more Dinitrol over the screw surface. They fit really well and honestly aren't going anywhere. It was immediately apparent that the road noise was reduced, even in the dry. I'd expect in the wet it will be even more effective. All in all it took well under 2 hours for both sides, including cleaning the arches and total cost with the screws and Dinitrol was £57.