It's kind of difficult for BizJets to get in and out of Farnborough or Oxford, or half the other airports they use in the UK, without going into Class G airspace. So it's not about "minimising costs".
They are also used to operating in many countries than the UK, where even quite major airports can be in Class E airspace. So VFR traffic can always be there. However, as with any other group of humans, there are variations in the standard of awareness and lookout.
I gave up reading airprox reports about twenty years ago, since there was virtually never anything constructive written.