I've found a market research report which has some really useful information for me, but the report itself is locked behind a paywall, and I've received no response to the mechanism for requesting a free copy.
My question is, can I just cite the info from the report's summary (it's actually still quite detailed) and if so, should I cite that as a separate source (webpage) rather than saying that I'm citing the report itself?
If you are able to read the information in the report, even if it was only in the abstract, you can cite it.
Cite the report and the complementary references you have found.
I would try to find an alternative first. Google Scholar often lists three useful links to entries: Cited by ..., Related articles and All ... versions. Checking them out often resolves the problem: you either get access to the material, or find an equal (or sometimes better) alternative.
Similarly, Crossref allows you to filter on the publication (Actions menu) helping to find an alternative.
In general, I also agree that reading the abstract and/or supplementary information is already a good reason to cite the source. However, I would strongly discourage to cite that web page unless you are absolutely sure it won't be gone in a matter of months. Maybe refer to the unique identifier such as DOI, or think about adding a WayBackMachine's URL of that site. Either way, it's safe to add a date when the webpage has been accessed (in the bibliography entry).
