Each year my sister and I spend a couple of weeks in London and vicinity in Sept./Oct. since she and her husband own a house near the Channel south of London. Since we do a lot of walking, regardless of the weather, I usually pack at least two pairs of shoes: one pair is a cream/grey oxford with a 1" heel and the other pair is a dark-grey bootie with a 2 1/2" heel. Both are 8-hour walking shoes for me and I waterproof them with a waterproof spray before I go.
If we are planning to go to the theatre, I'll sometimes toss in a pair of Fidji walking sandals with a 2 1/2" heel that I can wear for a more dressed up look. If we are planning to do more walking in the country, I'll pack a pair of light-weight, waterproofed, walking shoes.
I usually wear dark pants, top, scarf, boots, and jacket on the plane, along with my trench and my Longchamps tote bag. Inside my carry-on is a pair of jeans, another pair of pants, a skirt or dress, a few tops (with at least one long-sleeved and one dressy), a cardigan, a windcheater jacket, undies (including a silk cami which I can layer for extra warmth), and my toiletries. Since everything goes with everything else, I can travel quite easily for 3-4 weeks with this wardrobe.
If I do need something else, I can usually pick it up while I'm over there. Last year, in the first week in October, instead of the cooler, rainy weather that I thought we'd encounter, it was 30C in Brighton near the Channel. I had to pick up a pair of loose trousers and a sleeveless top from the summer sales rack. In previous years, during that same week, I've been layered up in my cami, long-sleeve shirt, cardigan, jacket, and trench with a scarf wrapped around my neck.
I also bring a smallish, nylon bag rolled up in the corner that I can use as checked luggage on my return to hold the goodies that I've purchased while over there.
If you need help putting together a travel wardrobe, I'd take a look at some the capsules posted at The Vivienne Files: http://theviviennefiles.blogspot.ca/
