"I can well see the challenge of vectoring jet traffic through very busy class G"
Are you serious? You make it sound like we're all playing in the same big sandpit. I'm sure it would be an issue if Gatwick, Heathrow, Luton, Stansted and City didn't have CTA/R protection and NATS deemed it essential to ensure separation, but they do have their own airspace to play in!
It's not as though we currently have jet traffic buzzing around below the London TMA at 2000' mixing it with the Cessna and Piper traffic!
The only stuff I sometimes hear/see is going into Southend.