* Wants more details on CVC/Cosmen bid, Stagecoach's plans
* CVC/Cosmen bid depends on keeping UK rail exposure
* Stagecoach may buy some of Nat Express if CVC acquires it
* Stagecoach shares down 2 pct, Nat Express up 1.2 pct
(Recasts, adds detail, analyst comment, closing shares)
By John Bowker
LONDON, July 27 (Reuters) - Britain's National Express is seeking details on the takeover proposal from the consortium of CVC and the Cosmen family and the plans of potential bidder Stagecoach.
The bus and train operator, which received an indicative proposal last week from 18.6 percent Spanish shareholder the Cosmens and private equity group CVC, said on Monday that the consortium's offer had a number of conditions attached to it, including the retention of two UK rail franchises, extensive due diligence and financing.
National Express also said it wanted more detail from rival Stagecoach, following a statement that it was in talks with CVC/Cosmen about taking parts of National Express if a bid was successful, while also mulling its own approach.
National Express shares closed up 1.2 percent at 350 pence a share, having earlier been up more than 4 percent as the market scented a deal. Stagecoach closed down 2 percent.
Andrew Fitchie, an analyst at Collins Stewart, said Stagecoach was most likely interested in National Express' bus operations in North America and the United Kingdom.
"It (Stagecoach) would have no interest at all in UK rail -- it has problems of its own there -- nor in Spain," he told Reuters.
Fitchie valued the company last week at 465 pence a share, valuing the business at 535 million pounds.
Cazenove's Edward Stanford said the company could be valued at anything between 400 pence and 530 pence.
"We expect a bid for National Express to emerge in due course and we believe that this will have to be in the region of 400p a share to have any chance of success," Stanford said in a note.
Fellow transport operator FirstGroup has already mooted and withdrawn an all-share deal, while newspaper reports have also named Go-Ahead as a potential candidate.
Go-Ahead declined to comment.
National Express is expected to publish key details of its future strategy as an independent company at its first half results on Thursday. It is also likely to argue that it is successfully managing a mammoth debt pile, which still at more than 1 billion pounds at last count.
HOLDING ON TO RAIL
National Express said the CVC/Cosmen consortium's proposal is subject to the operator retaining the East Anglia franchise, which runs between London and Norwich, and the smaller c2c London commuter franchise.
This would put the firm at loggerheads with the government, which said earlier this month that it would take back the loss-making London to Edinburgh East Coast franchise.
Transport Minister Lord Adonis has said he also wants to strip the firm of its remaining two franchises -- a move backed by the cross-party Transport Select Committee.
National Express disputes that the government is able to take the franchises back under state ownership.
Stagecoach said on Monday that it had held talks with the CVC/Cosmen consortium regarding the possible purchase of "certain businesses and assets of National Express" in the event that the consortium concludes a takeover.
Stagecoach, which is the operator of South West Trains, also said it will "continue to consider all other options in relation to National Express".
National Express declined to comment beyond its statement. Stagecoach could not immediately be reached for further comment. ($1=.6075 Pound) (Additional reporting by Matthew Scuffham, Victoria Bryan and Simon Meads; editing by Rupert Winchester and Karen Foster)