Can't get android 7 on galaxy s6
Updates are always rolled out in batches to different regions (even the same exact  model could be sold around the world). For your region (G920FBTU5DQA2 - BTU - United Kingdom), as SamMobile states, 6.0.1 is indeed the latest.

You could always manually flash firmware for the same model but for another region (listed on the same page) via Odin, at the cost of potentially losing your data (back up first) as well as certain region-specific optimizations.