If you're getting a new car on 0% finance
Then you've bought at the wrong time as finance costs money and if it isn't costing money at that time it's come from somewhere else, probably a lower deposit contribution or something.
I've nothing against RTI gap, I got it myself, but it's essentially just gambling - both you and the insurer is making a bet about whether the car will be written off. You can tell from how low the premiums are how likely it is you'll win that bet.