UPDATE 2-UK retailer B&M's shares dented by dip in quarterly sales

* Underlying sales at B&M fall in second quarter

* Says market “difficult and uncertain”

* First half profit up 32.5 pct

* Shares fall as much as 13 percent (Adds detail, analyst comment, shares)

LONDON, Nov 13 (Reuters) - British discounter B&M European Value Retail reported a dip in quarterly underlying sales at its main UK business, after warm spring weather pulled forward sales of gardening and outdoor products, leaving little stock left to sell in August.

Shares in the group fell as much as 13 percent on Tuesday, after the company said B&M store sales were flat on a like-for-like basis in its first half to Sept. 29, following a rise of 1.6 percent in the first quarter.

The company, which trades from around 600 B&M and 270 Heron Foods stores in Britain as well as the Jawoll chain in Germany, said growth had returned in September as new autumn/winter product ranges arrived.

B&M, a so-called variety retailer which sells everything from furniture to electrical goods to food, mainly in retail parks, also reported a 32.5 percent rise in first-half profit.

“Successful, profitable general merchandise discount formats are emerging in major markets as economic pressures and profound changes in retailing provide fertile conditions in which they can grow,” it said.

The group said like-for-like sales growth at the start of the third quarter had been similar to the first half.

“We think B&M was impacted by the warmer weather in Q2 which had a negative impact on retail park footfall,” said RBC Europe analyst Shelly Xie, estimating a second quarter like-for-like sales decline of about 2 percent.

The analyst noted that comparative numbers are much softer in the third quarter than the first half.

The stock was down 7.5 percent to 374.8 pence at 1110 GMT, valuing the business at about 3.8 billion pounds ($4.8 billion).

Despite the weaker revenue trends, B&M said it was “well placed” for the key Christmas quarter. But it cautioned the retail environment was “difficult and uncertain”, echoing comments last week from Marks & Spencer and Sainsbury’s .

Market researcher Kantar said on Tuesday grocery sales in Britain increased 2.6 percent in the 12 weeks to Nov. 4, with German discounters Aldi and Lidl showing much stronger growth than mainstream supermarkets.

The B&M group made a pretax profit of 115 million pounds ($148 million) in the first half, on revenue up 16.1 percent to 1.56 billion pounds. The interim dividend was raised 12.5 percent to 2.7 pence.

It said it was on track to open at least 58 B&M stores and 20 Heron Foods stores in the 2018-19 year.

Last month the group entered the French market with the 91.2 million euro ($102.5 million) acquisition of the 95-store Babou chain - a purchase which means the group is now in all three of Europe’s largest consumer markets.

($1 = 0.7765 pounds)