Everone on the American sites swear by little giant ladders made by "wing". Also available in the u.k. at a price.
http://www.ladders.com/I have 2
copies of these, plus a 3 section, plus small and large steps plus a scaffolding tower. I can fit all these in/on top of my opel van (minus the scaffolding), plus my water fed pole/100kg RO water, poles and wc equipment and my work tools at once.
Mine are only copies, so I wouldn't recommend them, however I oil them with a releasing spray & never put them on the roof. You could fit 2 sets in the back of a cortina when folded all the way down. Each one opens up to 3 metres, I picked them up from Lidl for 50 quid each. Safety rated 175 kg.