Dec 8 (Reuters) - K3 Capital said on Thursday it was in advanced talks to sell itself to U.S. private-equity firm Sun Capital Partners Group in a deal valuing the British professional services firm at 257.3 million pounds ($314 million).

Sun Capital Partners will pay 350 pence per K3 share in a possible cash proposal, a 16.6% premium to the company's last close on Wednesday.

K3 Capital, which had received expressions of interest from multiple entities, said the other parties were no longer considering a possible offer for the company.

The company may recommend Sun Capital's proposal unanimously should a firm intention be made, it said. ($1 = 0.8192 pounds) (Reporting by Sinchita Mitra in Bengaluru; Editing by Anil D'Silva)