Figure to back this up for anyone wondering: 9% last year: https://www.statista.com/statistics/550583/electricity-losse...

Quote: Every year, the United Kingdom loses a share of generated electricity through transmission. In 2021, transmission losses amounted to around 25 terawatt-hours, or approximately nine percent of the electricity supplied in the UK that year. Transmission losses stood above 30 terawatt-hours in the early 2000's.

Yes it does. A big gas plant is say about 44% efficient (i.e. 56% lost as heat) so 10% of that electricity getting lost in wires takes you down to 40% of the original input energy.

Heat pumps don't qualify for EU Renewable heat incentives if they get less than 2.5 SFP (COP averaged over the year's seasons).

You're possibly thinking of an Open Cycle gas turbine, where we burn gas, it spins the turbine, and the hot exhaust is lost energy. The UK has a negligible amount of this in electricity production and obviously with higher fuel prices there's ever less reason to use that small capacity. The 30GW or so gas turbine electricity in the UK is Combined Cycle, so the exhaust heat runs a secondary steam turbine bringing them up past 50% efficiency.