Help - I have to attend a black tie dinner, in the City, at a Livery Company. Dress code for ladies is knee length dress with no bare shoulders. I am (just!) 50, 5' 10, size 12/14, with silvery grey hair. I would prefer the dress to have sleeves, ideally just above elbow or 3/4 length and preferably a scoop/round neck, although V neck would be OK. I find black no longer suits my hair and skin colour - any suggestions for alternatives? I have Wednesday afternoon in central London to shop...