UPDATE 1-WPP tumble, weak miners weigh on Britain's FTSE 100

* FTSE 100 down 0.6 percent

* Miners weigh; WPP slides after H1 results

* Financials, weak pound supportive (Adds closing prices)

LONDON, Sept 4 (Reuters) - The UK's top shares index ended the session in the red on Tuesday amid growing trade war fears and as a drop among mining stocks and a fall in WPP shares weighed.

The blue-chip FTSE 100 index closed down 0.62 percent at 7,457.86 points.

WPP dropped 6.2 percent after the advertising company cut its profit margin guidance as the group restructures.

"1H results were slightly better at the top-line, and slightly worse at the margin level than expected," analysts at Liberum said in a note.

WPP's shares posted their biggest one-day fall in about 5 months.

A drop in mining stocks as copper prices declined was the biggest weight on the FTSE with Rio Tinto, BHP Billiton and Glencore down 2.1 percent, 1.9 percent and 1.8 percent. Despite WPP's decline, a rise across financials and a weaker pound also helped.

"The significantly weaker pound boosted the FTSE in the previous session, lifting it notably above its peers on mainland Europe. However, the UK index has been unable to hold on to that momentum," analysts at London Capital Group said.

Company updates were also in focus among mid-cap stocks. Shares in Halfords Group were up 6.9 percent after the automotive and cyclical products retailer reported a rise in underlying sales in a tough trading environment.

Halfords also maintained its full-year profit outlook.

Some analysts were a little hesitant to be so upbeat after the update, however.

"While the year has started well with a robust trading update, the shares are likely to remain in limbo until Graham Stapleton gives his first strategic update on 27th September and a clear view on the investment needed to return the business to profit growth," analysts at Investec said in a note, referring to Halfords' new chief executive.

Halfords shares are flat on the year. (Reporting by Kit Rees, additional reporting by Julien Ponthus Editing by Keith Weir and David Evans)