An invasion of naked white mannequins which began in Victoria Square has now spread to retailers across the city.   But this is nothing to do with the next episode of Dr. Who, it is part of Style Birmingham, an initiative to encourage shoppers to appreciate the vast choice of clothing and accessories offered by department stores, high street chains and independents.   At Great Western Arcade we have a healthy range of independents and when you are next strolling through take a look at our very own Style Birmingham mannequin on the 'catwalk' in Unit 33.