Issue resolved in another discussion.
I had no idea that you could use /echo to output to a custom window.
Both mirc.chn and WikiChip state that /echo is used on channel windows (#channel name) and status or active window with -s and -a respectively.
Similarily /window (and the custom window section) makes no mention of /echo, but does expressly state the use of /aline etc. causing the idea thatonly these must be used with custom windows.
Both those sources need a drastic update/clean up.