Hi Rohith,
Have the coolant temperature sensors been checked? It's strange that the engine is colder despite it working harder.
The 1.6 TDI has 2 sensors (many do not know this). When facing the car with the bonnet open, 1 sensor is located on the left side in a pipe going towards the EGR, the second is on the right side basically in the engine itself.
My recommendation would be to find someone who has VCDS (I'm happy to help if you're able to make it to West Yorkshire) and measure the live data from both sensors. If there's a big discrepancy, it's possible one of the sensors has gone. The fact that your fuel consumption is up and your engine temperature is behaving in the opposite way it would if there were a blockage makes it more likely to be a sensor issue.