We will get the excess back (I hope). I understand that about lads driving - trust me - I have helped teach both my son and daughter to drive and I know which is safer. I wasn't banging on - I was pointing out the difference in excess when it would have made no difference who was driving.
I don't know the full circumstances of the accident obviously but the excess thing is relevant. A 17 year old is a novice driver and a more experienced driver might well see a problem coming and react differently. Possibly not in your case but statistically that is likely hence the different excesses. If the excesses were not different then your premium would be considerably higher in the first place.
Most people think insurance is a pain (I should know, I worked in the industry for 28 years) but there is generally common sense in the reasons insurers do what they do.