Eastern European coffee shop operator Coffeeheaven is in 'advance talks' about a possible offer from Costa Coffee group Whitbread, the two firms confirmed this morning.Both companies issued statements saying they are in talks over a 24p a share offer.An early report in the Daily Mail said speculation over a 25p-a-share cash bid was intensifying.In June, Coffeeheaven, whose coffee shops are mostly in Poland, said it had started a strategic view to allow it to take advantage of acquisition opportunities, which in turn had 'initiated early stage preliminary discussions which may or may not lead to an offer being made for the company.'Costa Coffee operates hundreds of stores in the UK, but also has a presence in Poland, the Czech Republic and Hungary, where Coffeeheaven also operates.