Welcome @Ben_Goodwin 
Nice, this is a topic I’ve recently been really interested in!
On SerpAPI
Generally for SerpAPI because it’s google underneath, I found using Google Search Operators to be a powerful way to get closer to the results you want. So for your example:
site:<url>could scope to only sites you care aboutloc:<city>could restrict to a local region or city
So experimenting with something like:
(site:ebay.co.uk OR site:gumtree.com) loc:sheffield intitle:<part> (intext:"for sale" OR intext:"reseller") <price>
could help reduce the amount of manual filtering you’d have to do.
On Business Search
This is a tricky one but I would imagine you’d want to get these details from the local authority/gov website? Google map results are a great starting point but a lot of the time it’s autogenerated so data could be patchy. One approach could be to:
- Try to get company registration number off their shop page or terms & conditions on their website
- Do a search on a gov website or on a third-party company database.
Results could be mixed depending on how you’d go about scraping this information. Personally, I’d use an AI-powered website crawler for this task - definitely would recommend Oskar’s tutorial on his AI crawler for something like this.