I think you're allowed 6 points on a provisional, so you will probably still be OK license-wise. Yes your insurance will most likely go up now, and remain high when you pass your test. It will probably be a fairly substantial amount, next time pay more attention to your speed.
I wouldn't say your driving instructor is an idiot to be honest, he's quite right, it is your fault and has nothing to do with him really. He might have told you to slow down, but ultimately you're responsible for the vehicle on a public road.