I never did get round to running Wireshark and having my cousin analyse it, but recently I've changed ISPs which has forced me to move my Gerroa-Weather web page once again. I did the changeover yesterday afternoon, then ran a realtime FTP log overnight.
This morning I stopped it and looked at the (>14Mbytes) log file. I did a search for 'abort' and then one for 'error', but found not one instance of either. You'll recall that aborts were relatively frequent when running on the previous two websites.
So I'm happy that the problem has been solved by finding a professional web hosting company (who fortunately also provide my web hosting free of charge).
Steve, sorry if I cast any doubts on the performance of your (third-party) FTP routines – you're totally exonerated now!