You might be surprised by the insurance. Because most 17 year olds end up with a little hatchback of some sort, I think they're deemed to be a higher risk vehicle (aren't statistics wonderful) and prices get inflated as a result. Something unconventional can sometimes work out cheaper (relatively speaking). The fact that an old series is very much not a typical 'boy racer' vehicle might work in your favour.
I'd go for a 109. Right now everyone is after defenders (or 90/110) as production is ending, so a series would probably work out cheaper. Doing the restoration now would be a great project- good for learning skills and they get something to drive that you know is in good order.