The problem in the North of England is somewhat different, there is over capacity on many routes so yields are lower to start with, this part of the UK is very very price sensitive on bucket & spades routes.
People will readily fly at very unsocial hours to save a £5 a head, which is another £5 to spend on. Booze in the resort, many know that Ryanair is crap, but they can put up with being treated like dirt if they can save £20 a head ( or think they can) !!
Rather sweeping and inaccurate statment there really.
Let's not forget that the North West has the largest air market outside of London, with approx 32m passengers per year. That scale would not have been built up on crap yields for the pure s**t and giggles of it. Airlines are not charity cases.
Let's look at fares too shall we:, using Google flights as an example as it can be accessed by everyone easily
May 28th Malaga round trip for a few days:
LGW has the cheapest starting price of £156
BHX has the cheapest starting price of £133
MAN has the cheapest price starting price of £219
BRS has the cheapest starting price of £23
LPL has the cheapest starting price of £152
Same dates, Alicante:
LGW £156
MAN £185
BHX £233
BRS £171
LPL £168
PMI:
BRS £187
MAN £197
BHX £172
LGW £153
LPL £173
There is also a pretty similar story over the winter too on a fair few dates I looked at. Do those prices suggest that the north west singularly has an issue with yield? Overcapacity? Seems on par or better with the U.K. To be honest!
Also, one thing to consider is on board sales. For both Ryanair and Easyjet, the north west also has some of the best on board sales figures, which further boosts the airlines profitability. I know the southerners like to laugh at the Northern counties spending habits, but the airlines love it!