uk-egypt-sth africa overland

im trying to get this trip organised. start uk end of july. so far me and a mate (25 yr old kiwi guys) give us a yell if you are half interested.
give us a yell if you have done this before..
do i buy a car in uk? egypt? somewhere else
insurance?
does anyone know how much roughly this is going to cost?
im guessing it will take about 2-3 months?