我认为不需要签证，但还不能完全肯定, 规定如下

在英国使馆的网站上说，如果你是中国国籍，只要你持有美国，新西兰，澳大利亚的有效签证，途经英国去另一个国家或领土，就不需要过境签证。

这是转自英国官方网站，不过这个适用于在丹麦的华人

You asked if a national of China needs a visa to pass through the UK in transit.

Yes, you need a Direct Airside Transit (DAT) visa, unless you hold one of the following:

a valid visa for entry to Australia, Canada, New Zealand or the United States of America and a valid airline ticket for travel via the United Kingdom as part of a journey from another country or territory to the country in respect of which the visa is held;
a valid visa for entry to Australia, Canada, New Zealand or the United States of America and a valid airline ticket for travel via the United Kingdom as part of a journey from the country in respect of which the visa is held to another country or territory;
a valid airline ticket for travel via the United Kingdom as part of a journey from Australia, Canada, New Zealand or the United States of America to another country or territory, provided that the transit passenger does not seek to transit the United Kingdom on a date more than six months from the date on which he last entered Australia, Canada, New Zealand or the United States of America with a valid visa for entry to that country;
a valid USA I-551 Permanent Resident Card issued on or after 21st April 1998;
a valid Canadian Permanent Resident Card issued on or after 28th June 2002;
a valid common format Category D visa for entry to an EEA State;
a valid common format residence permit issued by an EEA State pursuant to Council Regulation (EC) No. 1030/2002;
a diplomatic or service passport issued by the People’s Republic of China; or
a diplomatic or official passport issued by India; or,
a diplomatic or official passport issued by Vietnam.

http://www.britishembassy.gov.uk/servlet/UKVisasDoINeedAVisa?url=%2Fservlet%2FFront%3Fpagename%3DOpenMarket%2FXcelerate%2FShowPage%26c%3DPage%26cid%3D1125563690119&purpose=Transit&nationality=China&location=Denmark

你可以查一下对在美的华人如何要求。

Good luck