The FTSE 100 has closed up 8.8 at 5083.
This was despite downbeat full-year results from mmO2.
Although the figures came in at the top end of expectations, the City was more worried about weak UK margins compared with rivals.
Shares, which are now at their lowest point since mmO2 demerged from BT last autumn, fell 5¾p to 42½p.
Along with mmO2, BT Group was heading south, falling 8½p to 276p.
But Vodafone, which yesterday reported the largest ever loss for a UK company, recovered some of the previous day's losses to gain 3p at 105¾p.
Other fallers included chip designer ARM Holdings, which slumped 7%, or 14½p at 187½p, after a broker downgrade on its stock.
Invensys was also under pressure ahead of its results announcement tomorrow. Shares fell 2p to 103¾p.
Leading the risers was Argos-owner GUS, up 6% after a 13% improvement in underlying profits and saying it was confident about the coming year.
It also confirmed plans to partially-float its upmarket fashion house Burberry in July. Shares rose 39p at 659p.