I think you'll need to become much bigger as you are, to be able to sell it to people.
I totally agree, people do prefer to buy cars locally, especially when they're non-specialised cars/vehicles, but Gumtree is free to advertise for private and trade (with the overly priced option to pay for featured ads), although being part of the eBay machine, it may not stay that way.
Personally, I never search for cars on Gumtree, I just browse to see what's been advertised over the last few days as it's not my preferred place to buy cars.
I love to see enthusiasm in the motor trade and people trying new things, but I don't see anything really different about CCG than what's already out there, and if it became a paid for site, I don't see the attraction at all, unless everyone knew the name.
I hope you see this as constructive criticism, I'm in the trade myself, and just don't see the dealers paying for more advertising/local lists than they already do, unless it's something special, I could spend a fortune with all the phone calls I get daily with people wanting to put me on a list. Maybe it's just my area, and it's booming elsewhere.