Yeah it's an easy tweak. All you gotta do is:

on *:text:!ukweather*:#: { ukweather $2- }
alias ukweather {
  ;the rest of code goes in here

Now, you can have this script trigger both ways via:
/ukweather for self-trigger and !ukweather for other people.

It still needs an edit for the $1 and $2 and $3