I noticed that replies here only relate to the USA and by googling my problem it seems that the cause is having a USA version of Thunderbird and so I need a UK version. I wondered do I need to delete my UK version of Thunderbird first?

I mean delete my USA version first?

I uninstalled my USA version and downloaded a UK 64 BIT (MY PC bit length) and it is now on a UK dictionary. Downside is I can't find my Thunderbird ICON yet.

I wondered if my old icon was still pointing to the old USA version so I deleted it. Then I found an exe file that launched Thunderbird from the downloaded files and made a copy and put the copied launcher for the Thunderbird mail from the downloaded Thunderbird files on the desktop and changed the icon to an icon from inside the downloaded Thunderbird list of files and that now works too. So if this helps any one else that's good but I seem to have found my own way around.