With all due respect OXF ATC ...
Why choose to make comparisons between Kidlington vs Biggin and/or Farnborough ... Because it suits you to do so per chance?
Biggin Hill has a court injunction in place preventing it from accepting commercial airline (fare paying passenger) movements, were such a court injunction not in place then, without a shadow of a doubt, Biggin would have improved upon it's opening hours, it's RFF category, it's public transport links, indeed just about everything, long before now.
Likewise Farnborough has similar restrictions on the type of movements it can accept!
Northolt also has restrictions but you opted not to compare that to Kidlington ... I wonder why ... One is ideally placed on the A40 and on the fringes of London whilst the other is placed way off the M40 and out the back of beyond someplace!
And why state that Kidlington's runway is strong enough to accept BBJ's & A319's ... Remind us again of the length of Kidlington's runway if you so please?