The chart on p60 of the Davies report shows the propensity to fly by region. Although the figure for Greater London is very high, that for the South East is not that much higher than for the North West. And the North West does quite well in comparison with other UK regions.
These number are relative to economic activity and are hardly surprising.
As said through the regional numbers compared to the South East (excluding the GLA) are more compatible.
I would also tend to be comparing and contrasting the North West with other regions of the EU having a similar economic mix of industry/service and finance as being more useful in attaining a measure of performance. and regional demand on services
You certainly can not start to compare with London a city containing in no particular order world denizens of finance,retail, tourism and the TV/Film industries - All generating travel demand and replicated in how many other cities on the planet ?