Ive won quite a lot of duplicate normal cars and it does indeed tell that youve already got them and can choose to sell them instead. Ive got about 17-18 HE cars and have only had the Metro as a duplicate, which hopefully sold overnight. 

All I get from spins is bloody credits! So where do I find that goliath race to rack up all the XP?
All I get from spins is bloody credits! So where do I find that goliath race to rack up all the XP?
What's the cheapest price for a digital copy?
Another 16 wheelspins and still no HE cars.
**** this game.
You only get the option to sell if you win a car on a wheelspin that you already have.