I want to buy a Finnair Y ticket on the A350 LHR-HEL which is cheap and called superlight campaign and when going through a dummy booking it lets me choose preferred seats for no fee as OW Emerald (which I think are in a separate premium economy cabin - great if so!) but seems to still want me to pay for a carry on bag. Does anyone know if I do indeed need to pay this? - I will likely only have a small rucksack with me not a 'full on' carry on so don't really want to shell out another £23 if I don't need to - thanks.