As a bit of advice with your listings, your titles are very misleading and you are violating policy with your wording. You can state what make and model the car is, but you can't add things like 'not M3, evo etc etc". You can only say what it is, not what it's not. That is keyword spamming and against the rules. If someone reports it, eBay is within their rights to remove it.

Also, out of 4 sales, you've copped 2 negs. If you get another inside 12 months since your last, you could lose your selling privileges. Not having a go at you, it's easy enough done when you don't have a high rate of feedback, but just giving you the heads up, so if it does happen, you know why.

One last thing, the car you currently have listed, is that the same one you are wanting to open the unpaid case for? If so, you can't relist until the case is closed as the original buyer may pay once the case has been opened against them.

Good luck with it all. It's horrible having non payers, especially when there's that much money at stake.