Yep in American English the popular brand name is Agribon, of course there are others. I just learned from Eliot Coleman in researching for my latest cold frame post that the material is called spun-bonded row cover fabric (what a mouth full).

I did use some of this material over the peppers underneath the hoop cover to keep them longer into the fall. It did help a lot and with a few warm days that popped out from the colder days we got some extra pepper growth and ripening, which wouldn't have been as pronounced without the fabric. Awesome!

But I chose not to use it in these tunnels for the new winter crops to keep things simple and because I wanted to see what would happen with just the plastic alone.

I've used agribon in urban agriculture quite extensively in hot weather (in Zones 9-10) and it also helps a lot there as well, to keep the temperature cooler in the summer months. It wasn't immediately intuitive to me but it works well in both extremes of hot and cold! Whereas with the plastic cover you'd bake your veggies in the summer if you kept it sealed.