My thoughts on these are (and by the way - Please don't take these comments too personally, I'm hoping they can be constructive for you, these are only my opinions)
Photo 1: Focus seems a bit shaky and the DOF is a bit too shallow, my eyes aren't comfortable to rest on the image - a bit more car in the frame and it would be better
Photo2: Doesn't look straight, but there are lots of angles going on, The car could do with featuring a bit more confidently - for example, get lower down and further back, lets see some more ground and wheels etc,.. The car almost seems to be an after thought in this one as it's not well placed - and the indicator is distracting.
Photo 3: I like this one a little more - However the Focus seems shakey and the BMW is sticking its nose in from behind,.. definitely not meant to be there in my opinion and really makes a mess of the picture.
Photo 4: This is a strange one, i'm not sure about this one but The other cars in the background ruin the picture as well as the person on the right looking straight at the camera. Perhaps get a little higher and straighter for this sort of picture - I like the concept.
Photo 5: Seems blurry to me, And the back end of the car is cut off which I really don't like, I wish i could offer more useful advice for this picture but I just don't think the composition is very good to start with,...
Photo 6: Something doesn't sit right about this one - perhaps it's the lowered kerb, I'm not sure, Looks blurry again and the angle of car make sit look like it was parked there by accident and ruined an otherwise great picture of some graffiti! I think you could do more with this however.
Photo7: I like this one, It's original, some good creativity going on here again, I would say that if you had managed (granted it's a difficult angle) to get a little more car in frame and lose the red barrier infront of the person it would be much better.
Are you shooting Manual or automatic? Try a different aperture for starters. And are you using a tripod at all? if not, get one - they're really really handy for this sort of picture. I love the concept behind these pictures, A very urban sort of feel to these,.. Very 'need for speed' lol.