Blue chip shares struggled for direction amid gloomy revisions showing the UK economy grew more slowly than first estimated in the first three months of the year.
Britain's economy grew by just 0.2% in the first quarter of 2017, lower than an earlier estimate of 0.3%, according to the Office for National Statistics.
The FTSE 100 Index slipped 5.3 points to 7509.6 in afternoon trading, as traders digested data that reflected how rising inflation is squeezing household budgets.
Spreadex financial analyst Connor Campbell said that "rising prices continued to take their toll on housing spending and the retail sector".
In London, Hungarian airline Wizz Air was the best performer in the second tier after reporting record profit, up 28% to €246m (£212.9m) in the year to the end of March compared to 12 months ago.
The budget airline, which specialises in flights to and from central and eastern Europe, carried 23.8 million passengers in the period, up from 20 million the year before. Shares jumped 12%, or 229p to 2175p.
The biggest afternoon risers in the FTSE 100 Index were 3i Group (+28.5p to 869p), EasyJet (+24p to 1368p), Unilever (+60.5p to 4273p), Royal Mail (+5.7p to 434.7p) and Convatec Group (+4.1p to 321.5p).
The biggest afternoon fallers in the FTSE 100 Index were Anglo American (-22p to 1062p), TUI (-18p to 1155p), Mediclinic International (-12p to 801p), BT (-4.3p to 312.6p) and Marks & Spencer (-5.2p to 388.2p).
The biggest afternoon risers in the FTSE 250 Index were Wizz Air (+229p to 2175p), Intermediate Capital Group (+85p to 892p), Evraz (+6.2p to 199.5p), Grainger (+8p to 269.5p) and Paysafe Group (+14.5p to 496p).
The biggest afternoon fallers in the FTSE 250 Index were Petrofac (-184.6p to 430.4p), Acacia Mining (-41.4p to 263.6p), OneSavings Bank (-33p to 434.6p), Amec Foster Wheeler (-37.2p to 496.8p) and Capita (-32p to 545.5p).