* Bailiff visit part of shareholder attempt to get a say

* Decisive board meeting set for Friday

* Bidders weigh last minute changes to offers - sources

(Adds details, context)

By Leila Abboud

PARIS, April 3 (Reuters) - French media and telecoms group Vivendi VIV.PA has rebuffed a new attempt by minority shareholders to get access to documents relating to its sale of French mobile operator SFR as the two rival bidders eye potential last minute changes to their offers.

Colette Neuville, who heads a French association representing the rights of minority shareholders, sent a bailiff with the backing of a judge to Vivendi's offices on Wednesday because an earlier request via letter to Vivendi's Chairman Jean-Rene Fourtou for more transparency on the SFR deal was rejected.

The episode shows how tense the 15 billion-euro sale of France's second-biggest telecom operator has become ahead of a decisive board meeting on Friday.

Vivendi is in exclusive talks with local cable group Numericable NUME.PA since March 14, but rival bidder Bouygues

BOUY.PA has tried to muscle back in. First, Bouygues raised the cash part of its original bid and then it told Vivendi that it could choose between the two bids.

Numericable and its parent company Altice have remained silent, saying only that they continue to negotiate with Vivendi.

France's market regulator, the AMF, on Friday called on all the companies to provide more information to the market about the sale process and the details of each bid. Only Bouygues responded with two statements this week that confirmed a break-up fee and another exit clause.

Vivendi on Wednesday night said that its lawyers opposed the shareholder group's request for the documents because of the "the extravagant nature of this procedure." It added that it would apply to a judge for a summary judgment against the shareholder group.

The board of Vivendi is expected to decide on Friday whether to finalise a sale to Numericable or open official talks with Bouygues, with which it has been barred from speaking since choosing Numericable as a preferred bidder.

Under French law, the board's decision does not have to be submitted to shareholder vote despite the fact that SFR is Vivendi's biggest unit and it brought it more than half of revenue and operating profit last year. Neuville's shareholder group has called on Vivendi to submit any sale to SFR to a vote.

Sources close to the situation told Reuters that Numericable and Bouygues could change their bids on Thursday with the aim of tipping the balance in their favour.

Numericable, which is backed by billionaire Patrick Drahi, is weighing whether to raise the cash portion of its bid and lower the equity stake, a person familiar with the matter said on Tuesday. Meanwhile, Bouygues continues to search for outside investors to help it raise the cash portion of its bid.

Numericable prevailed initially because its bid came out ahead on the criteria set by Vivendi's board - the total value offered for SFR, the speed with which it would allow Vivendi to eventually exit the resulting business, the amount of cash offered, a lower risk of a lengthy review by competition regulators, and impact on jobs.

Bouygues new offer addressed some of the board concerns, but continues to be hampered by Vivendi's view that a merger of France's second and third-placed mobile operators would likely run into problems with competition regulators.

Bouygues says the competition review would happen in Paris, citing a clause in European Union regulation that says local regulators take the lead when the companies involved in a merger earn more than two-thirds of their revenue within one country. Bouygues also enjoys the support of the French government, whose state-backed investment fund has put in 300 million euros to help it win SFR

But it remains to be seen whether Europe's top antitrust regulator, Joaquin Almunia, would seek to take the review to Brussels. According to a document prepared by France's permanent representative to the EU last month, Almunia's staff is tracking the SFR situation closely.

The competition office of the EU commission believes it has legal grounds to intervene to ensure that mergers that take markets from four to three mobile players are implemented in a consistent fashion. It is now reviewing such deals in Ireland and Germany.

People familiar with Vivendi's thinking have said the board is not eager to risk a lengthy competition review at the EU, which usually take 12 to 18 months.

Bouygues has given Vivendi the choice of two bids: 11.3 billion euros and a 43 percent stake in the new company, or 13.15 billion euros in cash and a 21.5 percent stake.

Numericable's offer includes 11.75 billion euros in cash and a 32 percent stake in the new company.

(Reporting by Gwenaelle Barzic and Sophie Sassard; Editing by Andrew Callus)

((leila.abboud@thomsonreuters.com)(+33 1 49 49 51 82)(Reuters Messaging: leila.abboud.thomsonreuters.com@reuters.net)(Twitter: @labboudles))

Keywords: VIVENDI SFR/