Drupal Weather module - getting it local & working

Having just taken on a primary role for running a local group's drupal website I have been looking to add a local weather forecast. After checking available modules it looked like the imaginatively named 'Weather' module (https://www.drupal.org/project/weather) looked like the best balance of features & being actively maintained.

Very easily installed, its quick to get going but a little more involved to get it as I wanted:

My requirement is simple - to have a forecast available on the front page for a specific location, West Ealing, where the local group is based.

Running drupal 6.22 on PHP 5.1

Upgrading this site to the latest 6.x release of Drupal seemed to go fine, but I started to get emails warning of cron failures. The specific error being recorded was

Fatal error: Call to undefined function json_decode() in myhostingpath/sites/all/modules/twitter/twitter.lib.php on line 258

Now, although I'd forgotten I'd even got a twitter account or that I'd got a twitter module installed, I assumed that disabling the module in mentioned would just have thrown a similar error for another module. So best to fix the problem.

So in the interests of helping anyone else who's (googled for and) got this problem here's how I've fixed it: