I tweaked the script after playing with Superresolution. The SR plugin doesn't really give better results with this source. But I found another Script called MSR, which uses MVTools and doubles the size. The final upscale to 1080p is done with nnedi3_resize16. I've decided to go with FullHD as it gives a better image. I also played with the sharpness function of nnedi3_resize16. It gives a sharper image, but it also enhances the noise and artefacts.

pic 1

pic2

http://screenshotcomparison.com/comparison/137817

http://screenshotcomparison.com/comparison/137822

http://screenshotcomparison.com/comparison/137820

pic3

http://screenshotcomparison.com/comparison/137810

http://screenshotcomparison.com/comparison/137827

http://screenshotcomparison.com/comparison/137811

pic4

http://screenshotcomparison.com/comparison/137800

http://screenshotcomparison.com/comparison/137828

http://screenshotcomparison.com/comparison/137802

pic5

http://screenshotcomparison.com/comparison/137806

http://screenshotcomparison.com/comparison/137829

http://screenshotcomparison.com/comparison/137809