LONDON, July 21 (Reuters) - Britain's biggest manufacturing union said on Monday it would a fight a decision by Ford Motor Co to shift production and about 1,000 jobs to its plant near Liverpool from its Solihull plant in the English midlands. Land Rover, a unit of the world's second-biggest automaker, told workers on Friday that it would shift production of the Freelander Land Rover to its Halewood Jaguar plant from around 2006.