The FTSE 100 fell into negative territory as weakness in utilities and healthcare stocks dragged on performance.
At midday, the blue-chip index was 0.1% lower at 7,166.
MID AND LARGE RISERS AND FALLERS
House builder Barratt Developments gained 2.8% after it unveiled a 19% rise in first-half profit driven by higher completions and stronger margins.
Rival builder Redrow climbed 0.7% on news it had declared a special cash payout to shareholders amid a 5% rise in first-half profit.
Plastics supplier Victrex was flat at £23.60 on announcing that its first-quarter revenue slumped, due to market headwinds, de-stocking and adverse currency movements.
Water utility Severn Trent advanced 0.2% after announcing that it would post a full-year performance in line with its prior guidance.
AstraZeneca dropped 1%, despite announcing that US regulators had granted orphan drug status for its treatment for hypereosinophilic syndrome, a rare condition that can damage organs in the body.
Financial services company Just Group added 3% as it posted a 15% rise in annual new business sales, buoyed by increased demand for retirement income products.
Brick maker Ibstock firmed 0.2% on announcing it had poached Tate & Lyle's Chrish McLeish to be its new chief financial officer, to replace Kevin Sims, who had decided to retire by year-end.
Industrial and electronics products supplier Electrocomponents gained 6% as it notched 6% growth in like-for-like revenue in the fourth months through January on-year.
High street lender CYBG revealed net annual interest margins hit the top end of its forecast range, sparking a 14.2% rally to 204.2p.
SMALL CAP RISERS AND FALLERS
Outsourcer Interserve was up 10.5% at 14.5p after agreeing a de-leveraging plan with its lenders, bondholders and pension trustees. There were also reports that the company received a letter from shareholder Coltrane Master Fund calling for a general meeting to dismiss nearly the entire board.
Broking house WH Ireland dropped 9.7% after it warned that volatile market conditions had hit revenue across all of its businesses, while its costs had also risen.