The unusually warm weather and the reluctance of households and businesses to switch on their heating because of record energy bills led Centrica to issue a profit warning yesterday.  The owner of British Gas also admitted that it had lost 200,000 customer accounts after it raised bills by almost a fifth in august.  The group is now expected to make a full year pre-tax profit of ?2.4 billion, compared with ?2.5 billion previously forecast. Shares in Centrica closed down 1.6 per cent at 290p on the warning.  Residential customers of Britain's biggest gas supplier have used on average 17 per cent less gas over the past 10 months compared with the same period last year, while electricity consumption has fallen by 3 per cent over the same period.  Business customers' consumption fell by 15 per cent for gas and 12 per cent for electricity. Centrica blamed the recent "unusually warm weather" and energy efficiency measures such as loft insulation and the use of energy saving light bulbs for the decline.  The average temperature in Britain for the first ten months of the year was 10.2C, one degree higher than the same period last year, according to the Met Office.  Mark Todd, a director of the price comparison site Energyhelpline.com, said: "People are increasingly turning down their heating to save money as they can't afford their energy bills. This trend occurred after the 2008 price rises and it appears to be happening again."  British Gas's average annual residential electricity and gas bill is now ?1,288, with average bills for all domestic consumers at a record ?1,345.  Centrica also hinted that more job losses could be on the way as a result of a cost-cutting review. This week it announced that 850 jobs from its energy services division would be cut, on top of existing plans to reduce the headcount by 270 elsewhere.  Energy consumption by households has been falling since 2005 as bills have risen and the Government's insulation programme has taken effect. But consumption rocketed last winter, one of the coldest on record.  Industry has been particularly badly