Shannons has choice of repairer, free windscreen every year, no hassle monthly payments of premiums (no extra charge). Shannons insure for TRUE agreed value (ie I said the value I wanted and they said yep, sure).
I've had no experience with JustCar other than obtaining a quote. Their "agreed" value was shite and they wouldn't insure my car for more than $20K (actually from memory it was around $18K).
If anyone needs help from Shannons, send a PM to Matt aka _8OO5TED_. He works for Shannons in WA and will do a good deal for SAu Members