Lowe, the UK doesn't have our fixation trucks, but the bedliner is aftermarket protection for the bed, can be a spray or thick vinyl. Optimum tested it on warehouse equipment (forklifts, etc) to check effectiveness and durability with great success. No reason it wouldn't work on your underside.
The Optimum Spray Bedliner has the following advantages for the consumer: UV stable, impact resistant, non slip surface, very hard to scratch or cut, thinner than it's competition, doesn't add too much weight to the truck. Also easy to repair if it should get damaged. For the installers, low equipment costs ($60 for the gun vs $15,000 for the mixing systems required by many others) easy and quick to apply, water based. Very easy to apply and no spray mist or what so ever which you will have with a normal paint job. The gun can easily be rinsed with water afterwards and it's ready for the next application,