After trading as much as 0.8% in either direction, the blue-chip FTSE 100 index closed 0.1% higher, helped by mining <.FTNMX1770> and food and drug retailer <.FTNMX5330> stocks but with a stronger pound weighing.
The domestically-focused mid-cap FTSE 250 index ended 0.1% lower, with shares in James Fisher and Sons tumbling 25.7% after a disappointing trading update.
U.S. Democrat Joe Biden took the lead over U.S. President Donald Trump in the battleground states of Pennsylvania and Georgia for the first time on Friday, putting him on the verge of winning the White House.
"The markets are taking this with a pinch of salt and perceive Biden's lead to be significant enough that any challenge won't be taken seriously or won't be enough to change the market," said Craig Erlam, senior market analyst at Oanda.
"We've seen four really strong days of gains and are just seeing a little bit of profit taking."
Both the indexes logged their best weekly gain since early June as the British government and the Bank of England ramped up stimulus measures to support an economy facing the impact of a second nation-wide lockdown.
New COVID-19 infections in England have stabilised at around 50,000 a day, according to an ONS survey, but the reproduction "R" number was unchanged at between 1.1-1.3, suggesting the epidemic had continued to grow in recent weeks.
Post-Brexit trade deal talks were also in focus with the European Commission President set to call British Prime Minister Boris Johnson on Saturday to discuss the negotiations.
EasyJet Plc fell 2.6% after further scaling back its already reduced flying capacity due to new lockdowns, while Aviva Plc gained 2.1% after German peer Allianz SE reported an unexpected rise in quarterly net profit.
(Reporting by Devik Jain in Bengaluru; editing by Uttaresh.V, Aditya Soni and Kirsten Donovan)
By Devik Jain