I observed same thing when I switched from Hathway to Tata Sky 2 years back. However, after making some adjustments on my 50 inch TV and STB settings, I got superb studio like picture quality. (after connecting hdmi 2.1 quality improved even further)
You will need to play with brightness, contrast, sharpness and color on your TV and on your STB try to experiment with 1080i and 1080p modes to see which looks better.