15kg is loads. If you didn't want to do any washing there, it's 10 pairs of socks & jocks etc, 1 pair of jeans, 2 pairs of shorts, 3 t-shirts, a couple of casual shirts and a light jumper. Wear something fairly light for the journey including a pair of comfy and non-smelling shoes/trainers. Maybe you could buy one of those packaway lightweight jackets from a camping shop and carry it with you all the time, I do and it (and the trousers!) have kept me dry on many occasions.