New version pending review... Rated 4 out of 5 stars
Unfortunately, this addon has been dead for a while. Thomas no longer seems to be keeping it up to date.
I've therefore uploaded a new addon under the ID: cy-GBemail@example.com
Please find it on the following link. It's still pending review from Mozilla, but I hope that they will be able to replace Thomas' version with this one when they get round to it.
Let me know if there are any problems (find my mail on the "meet the developer" link on the right).