The FTSE 100 erased early gains to slip 0.1% by 0750 GMT. Midcaps dipped 0.2%.
Ahead of U.S.-China trade talks this week, corporate news dominated market moves with LSE falling 6% after Hong Kong Exchanges and Clearing scrapped its unsolicited $39 billion offer as it failed to convince LSE management.
LSE shares, which dropped to levels not seen since September when HKEX first announced the takeover plans, are headed for their steepest one-day decline since the 2016 Brexit referendum.
Recruiters PageGroup and Robert Walters dropped 6.5% and 10.2%, respectively, after they revealed that a host of macroeconomic troubles including the U.S.-China trade war, Hong Kong protests and Brexit is hindering performance.
Rival Hays skidded 5.4% to the bottom of the midcap index.
EasyJet was the biggest drag on the index with a 4.6% slide, despite a robust outlook for the current year as the carrier said it expected capacity growth in 2020 at the lower end of its historic range.
A trader blamed profit-taking for the share price fall in easyJet, which said pilot strikes at rivals British Airways and Ryanair would bump up its revenue.
"The disappointment around the guidance will give the shorts a stick to beat them (easyJet shares) with... we think the industry is in better shape and we are more bullish," Goodbody analysts wrote.
British Airways owner IAG also lost 2%, while smaller player Ryanair gave up 3.3%.
The Sino-U.S. trade talks, scheduled for Oct. 9 and 10, could make or break stock market performance this week. However, mixed signals from Washington, including expanding its trade blacklist of Chinese companies, has done little to settle investor nerves in the run up to the meetings.
Market participants are still licking their wounds after a sell-off in global markets that had pushed the FTSE 100 to its worst week in a year as growth worries and recession risks peaked.