The £1000 excess wouldn't include the compulsory age related excess, so it is likely to be a combined total of closer to £1300!
My voluntary excess is £100, but I have £350 compulsory excess due to age, so £450 total.
That said, a £1000 increase to the excess, for a reduction of £690 on the insurance cost, is seriously worth considering at that age, but you are essentially gambling £300 if you do have a fault crash in that insurance year.
TBH that would be an option a lot of people might take at that age. I get them charging young drivers through the nose, the few I knew at 17-18 were utter lunatics lol.
Hell, even a "Your bill is £1500 for the year but if you get through then we'll give you 40% back" would work.
Of course, they don't have to do anything as people pay it anyway.