Review for British English Dictionary by 0bvious
Rated 4 out of 5 stars
I managed to get this to work. Install the dictionary, copy both the files it installs ('en-GB.dic' and 'en-GB.aff') to Program Files\Mozilla Firefox 3\dictionaries. Next, type about:config into your firefox browser. Search for all instances of "en-US" (or just "en-" if you want to find other dictionaries). Change all the instances of "en-US" to "en-GB" and hey presto! proper spelling is yours...
This review is for a previous version of the add-on (1.19).To create your own collections, you must have a Mozilla Add-ons account.