I he done Iceland Air and been quite happy. UK kid suggested it, as the benefit of going through Iceland instead of London or Amsterdam is that you rarely miss your connection, it’s all the same airline, moving all the people from North America to Iceland and from Europe to Iceland, then musical airplanes for the next destination. So, if your first flight is delayed, the airline generally seems to work around it. No sleeping in Heathrow!
PS: DH got upgraded to first class for the first flight, it was NICE. I did not get upgraded which made for some really amusing post flight stories