It's Lisa Rodgers you are thinking of, she's no relation to Cathy Rodgers who also produced the series. (and went in front of the camera to co-present with Robert for the next 2 or 3 series before Lisa joined).
There is a great book available all about the making of Scrapheap Challenge. I got it for Xmas a few years ago.
Yes - it's pretty much staged, including planting *useful" things for each build and the "spontaneous" design meetings around the blackboard, aren't! Very often they have gone well over the allowed 10 hours build time, otherwise the teams would have nothing to race/show/fight with.
Here's the book on Amazon;
http://www.amazon.co.uk/Behind-Scenes-at-Scrap heap-Challenge/dp/0752219995/ref=sr_1_3?ie=UTF 8&s=books&qid=1234185930&sr=8-3
Wow - 2001, didn't think it was that old!