FTSE 100 slips as oil majors, Diageo stumble

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* FTSE 100, FTSE 250 down 0.2%

* Homebuilder Berkeley up after trading update

* Supplier SIG drops after cautious stance on construction

Sept 6 (Reuters) - London's blue-chip shares dipped on Friday with losses led by oil majors and Diageo after a double rating downgrade, while investors were cautious ahead of key U.S. jobs data that would give further clarity on the health of the world's biggest economy.

The FTSE 100 index dipped 0.2% by 0711 GMT. The FTSE 250 midcap bourse was also down by the same level, pressured by building materials supplier SIG, which slumped nearly 7% after cautious comments on construction activity.

Spirits company Diageo was among the biggest drags on the main index, slipping 1% after Socgen cut its rating on the stock to sell from buy. Homebuilder Berkeley rose 1.7% after pointing to "robust" market conditions in London and the South East of England despite Brexit uncertainties. (Reporting by Muvija M and Shashwat Awasthi in Bengaluru; Editing by Bernard Orr)