UPDATE 2-UK's Aegis in $324 mln bid for Australia's Mitchell

* Mitchell founder to take significant stake in Aegis

* Offer 15 percent premium to Mitchell's last share price

* Mitchell board accepts cash and share offer (Updates with company statement, details of offer)

By Michael Smith

SYDNEY, July 29 (Reuters) - British media buying group Aegis (AEGS.L) has made a A$363 million ($324 million) takeover bid for Australian rival Mitchell Communication Group MCU.AX as it seeks to strengthen its presence in emerging Asian markets.

If the deal is approved, Mitchell's founder and chairman Harold Mitchell would become a significant shareholder in Aegis and would lead the combined Aegis Media Pacific business as Chairman. Mitchell, a high-profile media buyer, and his family currently own 40 percent of the target.

Mitchell shareholders would be offered cash or stock under the offer which values the Australian company at A$1.20 per share, a 15 percent premium to its last trading price.

Shares in Mitchell, Australia's largest media planning and buying group, shares were earlier placed in a trading halt after media reports in Britain flagged the deal.

Aegis Chief Executive Jerry Buhlmann, who was appointed to the top job in March this year, said he would use the deal to build up its existing Australian operations and its presence in the region.

"Mitchell is the leading marketing communications group in Australia, the eight largest ad spend market in the world, and this acquisition is a further step in transforming Aegis' operations in the Asia Pacific region," Buhlmann said in a statement.

Mitchell's board have recommended the bid to shareholders.

Shareholders can accept cash or shares or a combination of both under the offer.

Under the scrip component, shareholders will be offered 40 Aegis shares for every 67 Mitchell shares with a cap of 9.9 percent of Aegis share capital.

Mitchell shares last traded at A$1.04 on Wednesday, valuing the company at A$314 million or around 180 million pounds. (Reporting by Michael Smith in Sydney and Karolina Tagaris in London; editing by Balazs Koranyi)