Under 25 could mean anything. 17? 20? 24?

I think rating also plays a large part, you could be 30 with a rating 6 and be paying more than a 23 yo with a rating 1. The 25 YO age thing mostly has to do with your premium if you make a claim.

When I sold my R32 GTS-t I was 23 and paying around $900 for comprehensive with justcar on a rating 1. Even when I bought it at 20 YO it was only $1300 to insure.

You are obviously a high risk for whatever reason (driver history, car etc).

Depending on how modified the car is you might have to go through just car and get 3rd party. Most companies like AAMI etc won't insure heavily modified vehicles (ei engine swaps).

I hope you aren't driving without insurance, cos thats just stupid!

I am also so surprised at insurance Qs like this. Its really something you should look at before buying the car. If you can't afford the insurance you can't afford the car. Sorry to be blunt but its as simple as that.

Good luck with it.