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* FTSE 100 down 0.4 pct, energy stocks weigh
* Berkeley update, Barratt results boost housebuilders
* Investors cheer William Hill's U.S. deal
LONDON, Sept 5 (Reuters) - The UK's top share index retreated on Wednesday as big oil stocks fell, though housebuilders were a bright spot following comments from Berkeley Group about the London housing market.
Britain's blue chip FTSE 100 index was down 0.4 percent at 7,425.89 points by 0853 GMT, while mid caps were down 0.1 percent.
The FTSE's losses were in-line with a broader decline across European stock markets, which fell on the back of continuing worries over trade tensions and weakness in emerging markets.
"Emerging markets have been particularly weak and a lack of progress regarding international trade talks continues to unsettle investors," Russ Mould, investment director at AJ Bell, said.
A drop in the price of oil weighed on heavyweight energy stocks, with shares in BP and Royal Dutch Shell down 0.1 percent and 0.5 percent respectively.
However, Berkeley Group led UK housebuilders, its shares gaining 1.5 percent after giving a trading update.
Whilst Berkeley said that Britain's housing market was sluggish amid uncertainty over Britain's planned departure from the European Union next year, the company added that prices and demand in London were holding up.
London housing, especially towards the higher end of the market, has been a particular worry for investors in the sector given that foreign investors have previously been the driving force behind soaring house prices in the capital.
Additionally, peer Barratt Developments reported its full-year results, which included a 9 percent rise in pre-tax profit.
"Housebuilders have come off their highs on expected slower growth but the results we've seen so far from Redrow, Persimmon and Barratt don't really back that up," Neil Wilson, chief market analyst at Markets.com, said.
Among smaller stocks, William Hill was one of the strongest performers on the FTSE 250 as investors cheered its third U.S. deal in just over a month.
William Hill's shares were up 5.4 percent after signing a 25-year sports betting deal with casino operator Eldorado Resorts Inc.
"We believe that William Hill's share price has fallen too far and today's deal serves as a reminder that the group has an interesting option in the U.S. as well as more challenged businesses in the UK," analysts at Peel Hunt said in a note.
William Hill's shares are down nearly 19 percent so far this year.
(Reporting by Kit Rees, editing by David Evans)