The comment by the monarch spokesperson at the bottom of the BBC article is refreshing in these days where it seems impossible to get a straight answer:
By travelling via these Oceanic routes, the company avoids paying French and/or Spanish overflight charges and instead pays a much smaller Oceanic airspace overflight charge to the UK and Ireland..............Ultimately the environmental impact comes down to whether the travelling public is prepared to pay.
The travelling public can't have their low-fare environmental cake and eat it.
sr