Many thanks to Fifth Horseman:
Setting connections to weatherlink.com on seemed to do the trick.
(Somewhat counterintuitively as I'm not actually using weatherlink.com)
So if the logger is only able to transmit every minute I assume there is no point setting the interval that the logger sends to Wunderground at anything less than 1 minute?
And I also assume that there's no point in enabling RapidFire on the Wunderground config as it will onlyt send data every minute.
And my reasoning for connecting to WU via the logger rather than WeatherCat are the same as ocala sys. The logger will be permanantly live 24/7 bwhereas my computer may not be