PREVIEW-Sainsbury H1 profit seen up 16 percent, H2 tougher

* H1 results due Wednesday, Nov. 11 at 0700 GMT

* Underlying profit seen at 301 million pounds

* Asda Q3 sales due Thursday, Nov. 12

* TNS, Nielsen UK grocery market data on Tuesday, Nov. 10

By Mark Potter

LONDON, Nov 6 (Reuters) - J Sainsbury (SBRY.L), Britain's third-biggest grocer, is expected to post a 16 percent rise in first-half profit on Wednesday and flag a tougher second half amid falling food price inflation and stiff competition.

Data from market researchers TNS Worldpanel and Nielsen on Tuesday is expected to confirm Tesco (TSCO.L), Britain's largest retailer, is starting to regain market share following a big investment in its Clubcard loyalty scheme.

Third-quarter figures from Asda, owned by U.S. retailer Wal-Mart Stores Inc (WMT.N)), on Thursday are also likely to show another strong performance from Britain's second-biggest grocer, though it may also be feeling the effect of lower food price inflation.