In reply to andrew breckill:
I heartily recommend a really comfy mat.
I am a huge fan of the Exped Down Mat. It costs a FORTUNE, but is very very warm and very very comfortable.
If you are sleeping on the ground for any length of time, this will make a big difference.
And it will be really good for wild camping in the UK too.
As for prep, cardio, cardio, cardio.
It is not just about being able to do a big day. You want to be able to do a big day after you have already done three big days, and still be able to do another big day tomorrow.
I would also recommend you try to get as many multi-day walks done beforehand. Walks where you are camping. You want your camp craft to be slick. You want to be really really comfortable about living in a tent.
For info, I recommend Medex. Read their free book. Take it with you. Learn about altitude.
I also suggest a small first aid book, plus a set of medicines.
http://medex.org.uk//medex_book/english_version.php
http://www.amazon.co.uk/dp/1852847158/ref=asc_df_185284715811831725?smid=A3... is a good one.
Above all, be flexible, look for the moments of beauty and joy, and have a great time