If you just compare your fuel consumption you're not really going to get a reliable answer, because the heating load won't necessarily be the same for both periods.
I've run my heating continuously since October 2023, and compared the last two complete winters on continuous against the previous three winters with timed heating. The timer switched off the heating for 7 hours overnight, which amounts to a 29% cut in hours, and the fuel saving from timed heating that I've measured, with the fuel consumption normalised to the heating load, is about 8% (352W/K compared to 382W/K). This seems to compare quite favourably with the figure of 10% that I'd previously calculated using computer modelling.
Timed heating does save fuel, but not in proportion to the hours cut, because the relationship isn't a linear one.