Thanks your further help and fast response.
Followed your instructions to apply the patch. Got the error
"Patch can NOT be applied cleanly", which I noted, then continued.
The patch works, the checkbox "Disable automatic dashboard auto-update check"
does now stop WAN activity on dashboard page refresh, and can be toggled, which then
results in WAN activity and I assume allows the auto update to take place.
I've only done brief testing and not checked for anything else affected, however it looks like the fix is OK here.
J.