It is incredible the number of people selling instructions on how to build a dalek and more incredible that people are actually buying them.
They all claim to have diaries of their actual build, if so many people have actually built a dalek then why does the country no look like the battle of canary warfe.
Dalek builders are friendly folk who will probably give you the information free. Do a google for plans and diaries and you will get the information free, most of these items listed are copies of a 1970's radio times, which is widely available on the internet.
If you want to build a dalek, save your money (you will need it), what is for sale on Ebay are copied documents and diagrams that are available on the internet anyway.