HomePods connecting to wrong WiFi network - how to tell it to forget?

Having spoken to a member of Apple support on the phone, it seems that there may be a bit of a bug in the way that the homepods select their wifi network. I think they generally select the one that they know (have credentials for) that has the strongest signal. However, if they get onto a different wifi network, they lose the ability to control the homekit accessories (which are on a weaker but wider mesh network).

Seems a bit odd, and so what I've done for now is just to remove that strong (but unmeshed) wifi network from my iPhone's memory (which is where the Homepods get their knowledge of wifi networks from). Problem seems to have gone away, although it slightly cramps my style for the phone's options.