Try  Venco ClearX window restoration and protector. You don't need a company to do it for you as the crew can do it them selves. When you buy a kit i will come and show the crew how to do the pre-cleaning as this is the most important stage before the protector gets applied. Save thousands of euros. If the pre-cleaning gets done correctly the product should last about 10 months. The product will also work great for the shower doors.