Not something I would have done with a Jaguar, but each to their own. I think there are a few small errors though..
- The new arches and bumper look good, but don't go with the styling of the car. I think they look to, big?
- The wheels are good, but I am not sure on that rear one. It is meant to go like that, or is it because of the amount of low and the new arch?
- The background through the windows does not match this background. Try copy and pasting the windscreen from the old car in the background and brushing that to fit, of you could use the clone tool and add a bit of negative contrast. To fill in what would be there. That's what I always do.
Other than that, the background and the car are in the right perspective. Yes, the car could have done with some reflections, but hey- take it steady. Good job

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