* Revenue down 8 pct, beats analyst expectations

* Market conditions to remain challenging

* Post-trade revenues up 12 pct

* Stock rises 3 pct (Adds FT report in paragraphs 10 and 11)

By Daisy Ku

LONDON, July 15 (Reuters) - The London Stock Exchange (LSE.L: Quote, Profile, Research) saw revenues fall by less than expected in the first quarter, providing a boost for its new head Xavier Rolet as he starts cutting costs and lowering tariffs.

The three-centuries-old bourse, which is losing market share to a raft of aggressive newcomers, said on Wednesday that weak trading cut revenues by 8 percent in the three months to end-June, warning that the outlook remained tough.

"While market conditions are likely to remain challenging in the near term, the Group is taking actions to ensure we are in good shape and responding fast to changing markets," Rolet said in a statement, delivering his maiden results.

Trading platforms such as Turquoise, Chi-X, Nasdaq OMX (NDAQ.O: Quote, Profile, Research) and BATS are some of the low-cost newcomers in the market, as new European Union rules are forcing prices down and allowing them to rapidly gain market share.