It's near impossible to avoid them and unless you're driving without Tax and MOT, Insurance etc, I'd say you have nothing to fear. However, I do believe knowing their location is useful. For one, they're not just used for vehicle crime, but they're now being used to solve other crimes by 'coincidence' (oh he was in that area at the time).
The data is stored for 2 years.

There's already been a few cases of people wrongly arrested because their car happened to be in that area.

Anyway, I've had a go, let's see if it works :d

failed to open file.com ico_speedcams.bmp

Ok, so I wonder what I've done wrong. Hmm

Is there a correct way to encode image strips? I used that ipaq thing.

sounds like the file has become corrupted.
If you are not doing so already, use a old version of WinRAR (below 4.0).
work within the zip - don't expand. Under the file tab you will find the commands to copy/paste files from clipboard.
Using the ipaq explorer to convert back to the igo (RLE bitmap )format is as it is.
if you think that the problem is here try changing the strip image to a regular bmp format with a 256 colour palette , this I think should still work ,though I haven't tried this option myself

I've been using 7zip to edit the data.zip, should I switch to WinRar?

It's recommended. You can get winrar v4.01 here.

I'll give it a go. I think it is 7zip causing the problems

Turns out it was 7Zip after all. I'm now using WinRAR Unplugged, which is basically a portable version of 3.6 with no trial period. Works great