* FTSE 100 up 1 pct, mid caps flat
* Energy stocks, miners rise; pound weak
* Dechra Pharma says to implement hard Brexit plan, sharesslump(Updates prices at close)
By Kit Rees
LONDON, Sept 3 (Reuters) - The UK's top share index rose onMonday, starting September on a stronger note as a weaker poundand a bounce across commodity stocks helped British equitiesoutperform continental peers.
The blue chip FTSE 100 index was up 1 percent at7,504.60 points at its close, while mid caps were flatin percentage terms.
A rise in oil stocks contributed more than 21 points to theFTSE 100, the biggest sectoral boost to the index.
Shares in Royal Dutch Shell and BP were up1.9 percent and 1.2 percent respectively as the price of oilrose, supported by concerns that falling Iranian output willtighten markets once U.S. sanctions hit in November.
UK mining stocks also rose, with Glencore, BHPBilliton and Anglo American up as much as 1.9percent.
Other major stock markets across Europe were subdued onMonday, however, as investors fretted about an escalation in thetrade war between the United States and China, which had alsoweighed on Asian markets overnight.
"Investors still have mixed outlooks regarding the globaltrade situation as well as the turmoil in emerging marketscaused by the recent Turkish Lira crisis," Pierre Veyret,technical analyst at ActivTrades, said.
"This means fewer traders are going long on stocks rightnow."
A weaker pound was another factor keeping the FTSE inpositive territory. A fresh round of Brexit-related headlinesdented demand for the currency, as critics at home and abroadramped up their opposition to Prime Minister Theresa May's plansfor leaving the European Union.
A depressed pound lifted the FTSE 100's big, dollar-earningconstituents on the day.
However, worries over Brexit kept investors cautious on UKequities.
"The UK is a defensive, high-dividend yielding market whichmight have a problem if bond yields move sustainably higher, andif global equities advance, as we expect," equity strategists atJ.P. Morgan said in a note. They are underweight UK equities.
"We look for a stronger GBP, which will weigh on theperformance of FTSE 100."
Veterinary firm Dechra Pharmaceuticals was thebiggest faller among mid cap stocks, its shares tumbling morethan 21 percent. This was their biggest one-day loss sinceJanuary, 2003.
Dechra Pharma dropped after it said it would implement aplan to navigate a hard Brexit, adding that the measure mayresult in 2 million pounds ($2.6 million) of additional expense.
Analysts at Investec said that while Dechra's preliminaryresults were ahead of their expectations, they were introducingsome caution into their forecasts to reflect the potentialimpact of accounting standard changes, sanctions on Iran and ahard Brexit.(Reporting by Kit Rees; Editing by Kirsten Donovan and EdOsmond)