* Blue-chip FTSE 100 index flat by midday trading
* Miners under pressure on China growth concerns
* RSA up on expectations of averting more writedowns
By Atul Prakash
LONDON, Jan 6 (Reuters) - Britain's top share index was steady by midday on Monday, with weaker mining and retail equities cancelling out sharp gains in RSA Insurance on expectations it would avoid further writedowns.
RSA rose 6.7 percent after the Sunday Telegraph newspaper said a probe into its Irish business was expected to conclude that accounting problems were an isolated incident, and that no further writedowns would be needed.
Results from the investigation by PWC are due on Jan. 9.
The stock, the top gainer on the FTSE 100 index, also got a fillip from a UBS note raising its price target and adding it to the bank's most preferred list, traders said.
Gains in RSA helped the wider market to stay steady at the start of the first full trading week of 2014, with the blue-chip FTSE 100 flat at 6,731.75 points by 1132 GMT, despite a decline in miners and retailers.
The UK mining index fell 0.9 percent on new signs of economic weakness in China, a top metals consumer. Surveys showed growth in Chinese service sector activity slowing in December, mirroring the trend seen in manufacturing.
"China is slowing down, particularly on the construction and manufacturing side, and that could have a negative impact on the commodity space as China is a huge driver of commodities demand," Macquarie strategist Daniel McCormack said.
"If we do see a major slowdown in the country, then it would be difficult for the mining sector to do well. But that's not my base case as a major slowdown in China is quite unlikely. In the near-term, I would like to be positioned in industrials and techs and be cautious on miners."
Miner Fresnillo fell 2.3 percent to feature at the bottom of the FTSE 100 index, Randgold Resources declined 2.2 percent, while heavyweight Rio Tinto dropped 1.7 percent.
Retailers also weighed on the FTSE 100, which gained more than 14 percent in 2013, with Marks & Spencer down 1.8 percent to 435.90 pence on concerns that a trading update later this week may reveal weak Christmas sales.
"With the technical outlook deteriorating rapidly and with heavy negative media sentiment, I wouldn't be surprised to see further moves lower: 416 pence, which is the cycle low from June last year should act as support," said Jordan Hiscott, sales trader at Gekko Global Markets.
The market showed little reaction after the release of a survey showing an unexpected slowdown in the country's services sector growth last month. However, confidence rose and the economy was likely to have recorded its strongest expansion since 2007 last year.
"The outcome is softer than expected but the average of Q4 2013 data remains a touch higher than in Q3, a sign that the services sector has remained solid over the quarter," Newedge Strategy said in a note.