anyone undersealed their fabia?

Hello all

I recently bought a 57 plate Skoda Facia 2 as my first car. I intend to keep it for the next 5 years. I was looking underneath the car about a week ago and noticed in certain areas the underseal was pealing off in a few places around the sills and further towards the middle of the car. Does anyone know if it would be a good idea to underseal the car to protect the underside from further damage? I also heard that some underseals will damage the polymer coating already on the car so can anyone recommend to me a brand of underseal that's good?