So I've made some progress on getting supplies for this shindig. This time,clothing. Basically, I'm going to need so much stuff that I figure if I spread it out over the next few months it shouldn't hurt my pocket too much.
I went back to Kathmandu who were so helpful with the boots and socks. I got one pair of trekking trousers, plus 2 merino shirts and quickdry underwear and thermal leggings. The key here is to wear thin layers that are made of materials that are thermally efficient while also drawing sweat away from my body. In addition, I need to have things that have an anti-microbial element so they don't need to be washed as much (as laundry facilities will be in short supply) and will help to reduce the chance of fungal infections. I also need things that will dry quickly so that I can give them a quick scrub in the evening and hopefully they will have dried by morning.
So, as usual, they guy at Kathmandu was enormously helpful - giving me full information about what I need to take into consideration and telling me about all of my options so that I can make an informed decision. Top notch customer service.
PLUS, as a returning customer and because they know that I'm doing this to raise money for Bletchley Park, they knocked 30% off of the bill. So they take-home message is, please use Kathmandu for your trekking needs. They're really good people there.