Would it be possible for the OP or anyone for that matter to say a bit in general on the legal situation for a non-profit to extract data (and photos) from a commercial website and use this data to provide a free public service?
I know someone who has ideas in some other topical areas that would involve gathering and use of data from commercial websites and that's why I ask. Their ideas would provide a free and convenient public service and profit is not a motive.
It's a bit of a gray area, legally; data gathering in general. If you scrape a site at full throttle, it can stress it (like a DoS attack), making it perform poorly for real users.
Scraping is done everywhere though. Ethical scrapers, such as Google, throttle their traffic so as to not overwhelm a website. They also store the content and present it via the search engine results page. Really, when you think about it, it's no different to what I'm doing. Except nobody minds if Google indexes them. Or if they do they can configure Google to ignore their site -- which it honors.
In my case, I'm not ripping chunks of text, just data / history / numbers and providing a slightly different way to search them (and view them, with reports), and linking back to the original site (not trying to steal their traffic). I wouldn't steal a description and display it, as that is pure theft, totally unoriginal, and lazy, in my opinion.
I'm also not stealing the images, technically; I refer to the original. If RightMove take it down, I don't retain a copy and show nothing. However, linking images like this is probably unethical...don't know about it being illegal.
In general, don't take the p1ss and I think you'll be okay. Don't pass stuff off as your own that isn't, and you should be okay. Scraping a site and doing something new or interesting with the data, is not going to cause problems, I would bet.