It has been one year, since I calculated and invested into the loft insulation.At the time I spent about 750 GBP and 5 days to put the insulation up in the loft (including cleaning it and teak oil application to the beams and joists to protect them). I also estimated that 20% of the heat loses were going through the roof.
The actual natural gas consumption in 2016-2017 was 24,500 kWh (at 4.28p per kWh + 14.80p standing charge a day) or 1,104 GBP a year.
Since I installed the loft insulation 2017-2018 consumption was 16,400 kWh (at 4,46p per kWh + 19.18p per day) or 8,100 kWh less (30% reduction) at the cost of 760 GBP. This is a saving of 344 GBP a year.
This means that I will get my money back in just over 2 years. I overpaid my utility company by 500 GBP so far. Only after I contacted them, they bothered to cancel couple of the monthly payments to reduce their debt to me.
The natural gas prices went by 5% up in the UK last year, making them among the most expensive in western europe. No wonder that the propaganda encourages people do not heat their homes, including leaving some of the rooms unheated and keeping others at 61F (16C) in the winter.