I am also going to London this month with very limited suitcase room. With only 6 pieces I would have 9 outfits. I could even layer the denim shirt under the sweater for those extra chilly days.
I am going to Spain this month and am allotted only a backpack to fill with my clothing. This is essentially what I am packing. With only the 8 main pieces shown (not including the outerwear) you can get about 12 outfits. You could even tuck a dress into the maxi skirt if you wanted to get really clever!