I took the time today to treat my Copen to a bit of rust prevention. I've gone with Dinitrol products. Available from here; http://www.frost.co.uk/automotive-rust-products/dinitrol-rust-prevention.html 2 x S330 Dinitrol Cavity wax - for in the sills & inside the rear arches. 1 x Extension hose. 3 x S335 Dinitrol underbody wax - for the rear inside arches & floor plan. I also bought a tin of Hammerite Black Smooth from Halfords. First job, give the underside a good jet wash. Use a stiff brush to clean any mud off. Let it dry. On a flat solid surface jack the car up & support with axle stands. Make sure you loosen off the wheel nuts first. Take off the wheels & remove the front wheel liners. The clips that hold them on arn't too hard to remove. I also removed the front grill & bumper. Once you have the wheel arch liners off, finding all the securing bolts & screws that hold the bumper on isn't too hard. One bolt is hidden behind the number plate. Don't forget to disconnect the spots & indicators. Things don't look too bad. I gave all the surfaces a good coating of S335 Dinitrol underbody wax. I also painted the underside of the front chassis arm with the Black Hammerite. I also painted the metal strap that goes infront of the intercooler. I didn't take any photos of the underside of the body, but I gave that a good coating with the S335 Dinitrol underbody wax. Don't get any on the exhaust though. I didn't get do the rear arches yet. I'll add photos once I've done them. When you re-fit the bumper, don't forget to re-connect all the spots & indicators. Next is to do inside the rear arches & sills. In the front wheel arch, at the front of the lower sill, you'll find a square hole (just above the round plastic bung). This is perfect to feed the extension tube to the S330 Dinitrol Cavity wax. Before you spray any of this, if you've parked on your drive, protect your floor with plastic sheets. The wax will find it's way out of the holes in the sills & drip all over the floor. If you not bothered about marking the floor, don't worry. Push the extension pipe as far in as it will go & begin spraying. Slowly pull the hose back out.