UPDATE 2-Britain managing Huawei risks, has no evidence of spying - official

*Britain a key battleground for Huawei in Europe. LONDON/ BRUSSELS, Feb 20- Britain is able to manage the security risks of using Huawei telecoms equipment and has not seen any evidence of malicious activity by the company, a senior official said on Wednesday, pushing back against U.S. allegations of Chinese state spying. Ciaran Martin, head of Britain's National...