* FTSE 100 flat, trading volumes light
* Johnson Matthey, SABMiller up after results
* Miners hit by weak Chinese data
By Tricia Wright
LONDON, Nov 21 (Reuters) - Britain's top shares traded flat on Thursday as solid earnings from companies including Johnson Matthey offset concerns over the outlook for U.S. monetary policy prompted by the minutes of last month's Federal Reserve meeting.
Johnson Matthey, the world's largest maker of catalysts to control car emissions, rose 2.8 percent, the top FTSE 100 riser, after unveiling a 13 percent rise in first-half profit, helped by increased global production of cars and trucks.
"A strong set of numbers... The outlook remains slightly cautious but notwithstanding any more negative news in this space we expect to see some more earnings upgrades through the next couple of years led by a strong pipeline," said Atif Latif, director at Guardian Stockbrokers.
Results also lifted brewer SABMiller, which added 0.8 percent. "Despite lacklustre volume trends (plus 2 percent), it is encouraging to see the margin expansion and pricing trends in the company's key growth markets of LatAm, Africa, and Asia Pacific," analysts at Liberum Capital said in a note.
The FTSE 100 was up 2.62 points at 6,683.70 points by 1135 GMT, having lost ground in the previous two sessions, in light trading volumes at a quarter of the 90-day daily average. The index is trading around 2 percent below a five-month high of 6,819 hit on Oct. 30.
Market gains were kept in check by minutes of the Fed's Oct. 29-30 meeting showing bank officials felt they could start scaling back the asset purchase programme at one of its next few meetings if economic conditions warranted it.
The stimulus has proved a major driver for the UK benchmark index, which has risen around 20 percent in the past year as investors have moved out of safe bonds and into higher-yielding assets, such as stocks.
This has left the UK benchmark index trading on a 12-month forward price/earnings ratio of 12.7 times, above its 10-year average of 12 times, Thomson Reuters Datastream shows. Some traders reckoned a pullback was warranted.
"Although the markets knew (stimulus withdrawal) was coming, and to an extent has been priced in for a while now, I believe there is scope for a selloff as some traders look to close positions and lock in profits," Sanlam Securities' head of trading, Mark Ward, said.
Fawad Razaqzada, technical analyst at Gain Capital, said that the index has resistance to contend with in the form of a downward sloping trend-line coming in around 6,700.
Should the index break below current support in the 6,650 area, he reckoned it could succumb to potentially significant losses, with the 50-day moving average at 6,611 the first target, followed by 6,495, the 200-day moving average.
News of slowing factory growth in top metals consumer China also capped Britain's miners-heavy exchange.
Antofagasta, off 1.9 percent, was downgraded by UBS on Thursday, to "neutral" from "buy", with the investment bank citing concern over the outlook for copper.