Britain's FTSE edges higher with commodity picture mixed

* FTSE 100 up 0.6 pct

* Miners buoyed by China comments, data

* Oil pressured by Iranian output stance

* Old Mutual (Other OTC: ODMTY - news) rises on upgrade

* HSBC downgrades Admiral Group (LSE: ADM.L - news) (Updates with closing prices)

By Kit Rees and Alistair Smout

LONDON, March 14 (Reuters) - British equities edged higher on Monday but underperformed euro zone shares as a fall in the price of oil weighed on energy firms and counteracted a fading boost to UK-listed miners from well-received Chinese data.

Britain's FTSE 100 index closed up 34.78 points, or 0.6 percent at 6,174.57 points.

Assurance from a top securities regulator that China will not reintroduce a circuit breaker mechanism to stop volatility on its stock market in the next few years cheered investors, as did some aspects of generally weaker Chinese data.

Copper stabilised below four-month highs and miner and commodities firm Glencore (Xetra: A1JAGV - news) was among the top gainers, up 4.4 percent, although the drop in oil prices curbed gains in the sector.

The FTSE 100, which is heavily weighted in oil shares, underperformed continental indexes, and the energy sector trimmed nearly 3 points off the index.

Brent crude dropped nearly 3 percent, below $40 a barrel, after Iran dashed hopes of a coordinated production freeze any time soon.

"Iran remains intransigent on the issue of an oil output freeze... (and) suggestions that oil has found its bottom may have been a bit premature," Connor Campbell, analyst at Spreadex, said in a note.

Shares (Berlin: DI6.BE - news) in South Africa-facing insurance company Old Mutual rose 3.9 percent on a price target upgrade from Barclays (LSE: BARC.L - news) , which cited full year results and good operational momentum.

Aberdeen Asset Management (Other OTC: ABDNF - news) , also exposed to emerging markets, was up 7 percent with help from China. However, more domestically exposed financial stocks struggled.

Insurers such as Standard Life (LSE: SL.L - news) and Aviva (Other OTC: AIVAF - news) , financial services group Providential and Barclays (Swiss: BARC.SW - news) were among top FTSE 100 fallers, with traders citing speculation that UK finance minister George Osborne may raise taxes on the insurance and finance sectors in his annual budget on Wednesday.

Car (HKSE: 0699-OL.HK - news) insurance provider Admiral Group fell 2 percent after HSBC cut its rating on the stock to "hold" from "buy" on valuation grounds.

HSBC also downgraded its rating on British mid-cap Stagecoach Group (Other OTC: SAGKF - news) on concerns about weakness in the rail industry. Shares in the public transport company dropped 5.4 percent. (Editing by Ruth Pitchford)