Id stitch a few pics together to get a higher resolution so it doesnt need to be enlarged too much, i.e. photo of head and shoulders, one of body then one of feet, not hard to do these days, this way the quality should be more than what you need for a life size print, Ive used these before and they often have deals on
http://www.posterxxl.co.uk/cgi-bin/xxl.cgi?r=y&c=uk