* Consortium offers 450 pence/share in cash
* National Express board is evaluating proposal
* Equity fund-raising also being discussed
* Arriva does not rule out offer
* National Express shares up 3 percent, pare earlier gains
(Adds Arriva comment, detail)
By John Bowker
LONDON, Aug 27 (Reuters) - British bus and rail operator National Express has received an all cash offer worth about 600 million pounds ($972 million) from a group led by its Spanish main shareholder, as rivals eye the debt-laden company.
National Express said on Thursday the consortium, which includes 18.6 percent shareholder the Cosmen family and private equity group CVC Capital Partners, had made a revised proposal of 450 pence a share in cash.
It added that it was evaluating the proposal, but also said it was discussing a potential equity fundraising with investors. An industry source said the firm was gauging shareholder sentiment as to whether they preferred the bid proposal over a rights issue, which would be used to pay down the group's near 1 billion pound ($1.62 billion) debt.
National Express shares rose nearly 8 percent in early trade, but were just 2.6 percent higher at 410.8 pence by 1207 GMT, their highest level since January.
"I think 450 pence is a reasonable number, although the share price suggests shareholders think the bid may not succeed," said Gert Zonneveld, transport analyst at Panmure Gordon.
"They must ask themselves whether they want jam today -- cash -- or support a company with an unproven management through a rights issue," he added.
Analysts have been saying for months that a rights issue of around 400 million pounds would be the best way to alleviate the National Express debt problem, short of selling the company or one of its main assets.
National Express, which also operates bus services in North America and Spain, ran into trouble earlier this year after passenger growth on its flagship UK East Coast rail franchise failed to live up to hopes, leading to substantial losses.
The group is planning to hand the franchise back to the government later this year, while Chief Executive Richard Bowker has resigned from the company.
The government is also keen to take back two further rail franchises that National Express wants to keep. CVC-Cosmen, which must make a formal bid by Sept. 11 or walk away, has said its offer is conditional on the rail franchises being retained.
OPPORTUNITY
The CVC-Cosmen bidding consortium does not include rival UK bus and rail operator Stagecoach, a source familiar with the matter told Reuters.
Stagecoach said last month it was in exclusive talks with the consortium about buying some National Express assets if the offer is successful.
"We can confirm that our position remains as outlined ... on July 27. We will issue an further statement as appropriate," a spokesman for Stagecoach said.
Arriva, another UK transport rival, said on Thursday it had also not ruled out joining the bidding.
"We will evaluate the situation and see if there is an opportunity there that we may want to get involved in," Chief Executive David Martin told reporters at the group's half-year results conference.
In June, National Express rejected a proposed all-share bid from fellow bus and rail operator FirstGroup, which operates Greyhound buses in the United States.
FirstGroup said last month it was not in a position to make a formal offer and a spokesman declined to comment on Thursday.
(Additional Reporting by Quentin Webb, Editing by Richard Hubbard and Erica Billingham)