Hi there, are the 469cM and 402cM matches with your Mum, rather than your gran?
If you're stuck on Ancestry matches for the time-being, you could try uploading the DNA to MyHeritage. You pay a one-off fee to unlock the tools but then you can see all the people you and a match share DNA with (Ancestry only shows this for matches above 20cM). It also has a chromosome browser which allows you to group matches on the same section of chromosome (called triangulation, and there is an 'auto-cluster' function which does some of this for you).
The database is smaller than Ancestry's and, just a personal thing, I don't find it as user-friendly as Ancestry, but I've had some big wins on there with high cM matches who haven't tested on Ancestry.
Family Fanatics has a YouTube tutorial for MH which might help.
https://www.youtube.com/watch?v=Vql0AXbtI6w