I'm not certain how profitable the airports division of PH is (I recall the whole Group pasted reduced profits last year).
With so much emphasis being placed on (a) profit and (b) Robin Hood Doncaster Sheffield International because of it's long runway, one can envisage Sheffield City and Barton being squeezed out unless users are willing to pay the arrogant and unrealistic prices demanded.
The of course, you have the land and the rest is predictable.
The real question will be if they can attract big commercial volumes into RHDSI and JLL airports to make these pay.
Who's expanding at present (not many).
Who's expanding the most (low cost carriers).
Do low cost carriers pay penal landing and handling charges (not in their business model).
So running airports is not such good business for new start ups.
The best place for GA is in the old military fields from the expansion period, where they still have enough runway left from agriculture. The facilities may not be swish but at least they get lots of movements to pay the finance charges on the land.
This could leave GA a rural sport (to replace foxhunting etc perhaps ??)
h-r