The export-heavy FTSE 100 ended 0.6% lower on declines in pharmaceutical <.FTNMX4570> and bank <.FTNMX8350> stocks.
The mid-cap FTSE 250, considered a barometer for Brexit sentiment, added 0.3% after sources and documents said the European Union and Britain were set to continue negotiations on a Brexit trade deal beyond an Oct. 15 deadline set by Prime Minister Boris Johnson.
"The fact that talks are going to continue suggests there is appetite on both sides for a deal and removes a certain amount of anxiety because there is no immediately pressing deadline to worry about," Connor Campbell, financial analyst at Spreadex, said.
After riding a global surge in equity markets on hopes of more stimulus, the FTSE 100 has come under pressure this week on growing domestic political frictions about new coronavirus restrictions to contain a surge in infections.
Johnson on Wednesday resisted a national lockdown and said he would stick to his localised approach, responding to opposition leader Keir Starmer's demand for a temporary national shutdown.
In company news, money manager Ashmore Group Plc jumped 7.7% after the company said a rise in assets under management during the first quarter more than offset net outflows.
London-listed shares of Just Eat Takeaway.com NV rose 6.4% as the food-ordering company reported a 46% jump in its orders during the third quarter.
Britain's biggest homebuilder, Barratt Developments Plc gained 1.7% after posting a near 17% jump in forward sales for the past three months, helping the broader sectoral index <.FTNMX3720> gain 0.3%.
But online fashion retailer ASOS Plc tumbled 10.3% as it said it was cautious on the outlook for consumer demand.
(Reporting by Devik Jain in Bengaluru; Editing by Rashmi Aich/Uttaresh.V/Jane Merriman)
By Devik Jain