By James Davey and Mark Potter

LONDON (Reuters) - A trading update from Wm Morrison next week is likely to see the supermarket emerge as one of the winners of the Christmas period, while one from Kesa Electricals is expected to place it firmly in the losers' camp.

On Thursday, Morrison (MRW.L), Britain's fourth-biggest supermarket group, is forecast to emerge at the top end of the grocers' Christmas performance table, reinforcing a trend that has seen cash-strapped Britons embrace chains with reputations for low prices over upmarket rivals.

In contrast Kesa (KESA.L), Europe's third-largest electrical goods retailer which trades as Comet in the UK and Darty in France, is forecast to report a big fall in underlying sales on Tuesday, highlighting how purveyors of big ticket items are continuing to struggle.

The blizzard of trading statements so far this month has shown there was no collapse in spending over Christmas, as some had predicted. The trend has been for discount and food retailers to outperform, while discretionary spending is suffering.

Morrison will report a rise in sales from UK stores open at least a year, excluding fuel, of between 7 and 8.5 percent for the six weeks to January 4, with an average of 7.6 percent, according to a Reuters poll of seven analysts.

In December the group reported growth of 8.1 percent for its third quarter to end-October

"It would be reasonable to expect some deceleration given tough comparatives, although the business has remained extremely promotional," said analysts at UBS in a research note.

So far J Sainsbury (SBRY.L), Britain's third-biggest grocer, has posted underlying sales up 4.5 percent for the 13 weeks to January 3, outshining market leader Tesco's (TSCO.L)'s 2.5 percent rise for the seven weeks to January 10.

The UK's number two grocer Asda, owned by U.S. group Wal-Mart (WMT.N), does not publish numbers until February 17. But it has said it enjoyed one of its strongest Christmas sales seasons and implied its fourth quarter to December 31 outcome would surpass the 6.9 percent growth reported for its third quarter.

Data from market researcher TNS Worldpanel on Tuesday showed Morrison was the fastest-growing UK food retailer in the run up to Christmas.

It said Morrison's sales rose 9.7 percent in the 12 weeks to December 28 against the comparable period last year, outperforming a grocery market growing 6 percent.

Morrison shares have outperformed the DJ Stoxx European Retail Index .SXRP by about 8 percent over the last year.

KESA GLOOM

Kesa is expected to report a drop in like-for-like sales of between 6.5 and 8.8 percent for the 10 weeks to January 3, according to a Reuters poll of five analysts.

Its statement is expected to echo the gloomy tone of bigger rival DSG International (DSGI.L), which trades as Currys and PC World in Britain, UniEuro in Italy and Elkjop in Nordic countries.

It posted a 10 percent fall in like-for-like sales for the 12 weeks to January 10 on Thursday.

Shares in Kesa have halved over the past year as sliding house prices and soaring unemployment have put people off buying fridges and washing machines. Worries over rival Best Buy's (BBY.N) entry into Europe has also dented sentiment.

Analysts expect British luxury goods group Burberry Group (BRBY.L) to report a fall in retail, wholesale and licence sales when it updates on third quarter trading on Tuesday, hit by industry-wide promotional activity and high exposure to Spain and the United States.

But a shining star of the festive season is expected to be ASOS (ASOS.L), the AIM-listed British Internet fashion retailer, which updates on trading on Monday.