I know many will probably give more better answers. I like my Paramo Cascada for UK. Though you might need something like Enduro (which I think is thicker).
There is Berghaus Deluge, though they are overtrousers, (so you need a base trousers underneath), are fairly cheap. Though, maybe other more experienced posters, can advise if the above is suitable for Iceland.
I've worn the above in cold conditions ok. Though, I do run hot!