This is not true, third party will cover other vehicles even if its a multi-vehicle accident, they just don't cover your car, so it is worth getting third party, definitely not worth getting comprehensive. Trust me, I've been through the same situation, you better of leaving money slowly on the side in case you have an accident, there are a crap load of parts for skylines out there. Even if you totally write of your car you can strip it and sell it. Just get 3rd party and be happy with it, honestly full comprehensive is not worth the financial burden.