Britain's FTSE edges higher with commodity picture mixed

* FTSE 100 up 0.3 pct

* Miners track metals prices higher

* Oil pressured by Iranian output stance

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

* HSBC downgrades Admiral Group (LSE: ADM.L - news) (Adds quote, detail)

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 rose 19.11 points 0.3 percent to 6,158.90 points by 1250 GMT.

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

These positive signs from the world's biggest consumer of copper and iron ore lent a steadying hand to the price of copper, which stabilised below four-month highs.

Miner and commodities firm Glencore (Xetra: A1JAGV - news) was among top gainers, although gains in the sector were reduced as attention switched to a drop in oil prices.

The FTSE 100, which is heavily weighted in oil shares, underperformed continental indexes, and the energy sector trimmed 10 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 3.2 percent on a price target upgrade from investment bank Barclays (LSE: BARC.L - news) , citing the company's full year results and good operational momentum.

However among the fallers, car insurance provider Admiral Group fell over 1.7 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 5.8 percent. (Editing by Catherine Evans)