Just posting to say issue is now resolved. Updated to wireplumber 0.5.1 today but it seems the fix is an updated config from the ArchWiki guide. The previous pipewire node suspension section (5.1.13) in the ArchWiki called for two seperate disable suspension configs for alsa monitor (in wireplumber.conf.d) and bluez (in bluetooth.lua.d) in two different folders.
The updated config now calls for a single config file in a single folder, namely: ~/.config/wireplumber/wireplumber.conf.d/51-disable-suspension.conf
In short, I deleted all previous configs, updated, placed the new single config file as per the updated ArchWiki article then restarted pipwire and wireplumber services. All working again without any issues.