Broker tips: Tesco, Persimmon, M&S, Interserve

After an "unimaginatively bad 2014", things are starting to improve at supermarket giant Tesco after a much better-than-expected Christmas trading performance, according to analysts at Shore Capital.Shore retained its 'hold' recommendation for investors, but said that measures being taken by new chief executive Dave Lewis to shore up the balance sheet should lower the likelihood of a near-term rights issue. Meanwhile, Hargreaves Lansdown Stockbrokers said that the current consensus rating on Tesco of a 'sell' is "unlikely to budge" for the moment but said: "Perhaps, at last, there are some glimmers of light at the end of the tunnel."Credit Suisse has downgraded its rating for Persimmon from 'neutral' to 'underperform', saying that the shares are overvalued, as it cut its target prices for stocks across the UK housebuilding sector."There has been a lot to like about the Persimmon equity story in recent years, and we remain of the view that it is a quality operator. However, we believe valuations have reached a point that we cannot justify," said the bank's Harry Goad and Samuel Thomas. They said that valuations in the sector are 75% more expensive than their 20-year average, and Persimmon's premium to the sector has expanded to 25% from 10% historically.Despite Marks & Spencer's disappointing Christmas trading update on Thursday, brokers Investec and The Share Centre have retained their 'buy' recommendations on the stock.Given the number of issues in different areas of the business, it is perhaps remarkable that full-year profit guidance was maintained," said The Share Centre's research analyst Ian Forrest. Investec said that the stock's current valuation does not reflect the company's "gross margin opportunity and shift to cash generation".Broker Numis said trading at support services and construction group Interserve was in line with expectations, though it lowered its 2015 earnings estimates by 3% to 63.1p per share because of higher investments."We retain our target price and move back to 'buy' following share price weakness which we believe reflects (unmerited) Middle East concerns on the back of lower oil prices," Numis said in a note.