News of a sharper-than-expected fall in UK retail sales last month hit the value of the pound on Friday.
Retail sales dropped 1.9% in December, the biggest monthly fall for more than four and a half years.
The FTSE 100 share index closed 10 points down, or 0.14%, at 7,198.44.
BT Group gained 2.41%, making it the second biggest riser on the index.
Investors appeared to welcome the announcement that it would raise prices for its broadband and landline services, while television customers will start having to pay for BT Sport.
The biggest was loser on the blue chip index was AstraZeneca, which fell by 3.36%.
On Thursday rival firm Bristol-Myers Squibb said it was not going to seek accelerated US approval for a combination of its two immunotherapy drugs as an initial treatment for lung cancer.
AstraZeneca’s shares were hit because it has similar drugs in development.
Royal Mail shares closed down 2.01%, as investors continued to react to Thursday’s news of a further decline in the number of letters being delivered.
Royal Mail shares had fallen nearly 6% on Thursday.
On the FTSE 250, shares in chemicals maker Synthomer jumped by 12.4% after it raised its profit forecast for 2016, saying it expects to report pre-tax profits of about £120m.