You say you 100s of DNA matches to sort thru
But there are ways of narrowing down search parameters using the filters
For example use location search + colour code all matches with London connection
You can also have a colour code for particular surnames found on trees
The option of tree owners surname can be useful
But I prefer surname found on tree
Look at tree of highest match + try the filter search with surnames of each of their great grandparents
https://www.rootschat.com/forum/index.php?topic=862688.0
I'm often finding new features at Ancestry.com that I wasn't aware of, so I'm not going to say that doing the above is impossible, but I have no idea how to do it yet. There's 10,000+ DNA matches, but less than 200 show up on the map. I don't see any way to search by location of people in the tree of those matches. The only search by name is a blanket search of a given surname against anyone in the tree of a DNA match or against the surname of a DNA match themselves.
Something complex like finding a DNA match to someone who has a great-anything grandparent who lived or was born/died in a specific town seems impossible. I think Ancestry would have to allow direct access to SQL queries to do that, but as far as I can see there's no API for the public. (I programmed SQL databases for about 3 years. I'ld be able to use direct access if it were available.)
And repeatedly the most interesting possible links turn out to be behind private trees, and our success rate at asking for access has been dismal. We've made ours open but people seem unwilling to reciprocate.
I'ld love to try the things you're suggesting but either you're used to a different DNA service with more useful search options, or more likely, my difficulties are because I still have a long way to go to learn the tricks to use Ancestry's one because they're not obvious to me - for instance, I did just in the last 10 minutes discover the "Shared Matches" tool and that has opened up the possibility of a whole lot of new insights. So I'm getting there slowly...
G