LO link to dictionaries not working

I have LO 5.1.4.2 for Ubuntu, but running in Linux Mint Cinnamon 18.1
I have an EN-US dictionary installed, but want EN-GB. When I click on the LO link in Spelling>Options to get more dictionaries online, it goes to a 404 page.
Trying searching the website does help for me as it mentions “extensions for EN-GB”, but I just don’t know if that’s what I want? I thought it would just be a dictionary, not an extension? I’m worried I might install the wrong thing.
Can someone provide a link to find what I need please?

https://extensions.libreoffice.org/

Spellcheck dictionaries are distributed as extensions.

This is the extension that I use that provides English GB/UK spellchecking: English dictionaries for Apache OpenOffice

The extension is for both Apache OpenOffice and LibreOffice. To install:

  1. Download the spellchecker extension package. This will give you file titled “dict-en-[date].oxt”

  2. Open LibreOffice Writer then go Tools (menu) > Extension Manager…

  3. Once the manager opens just click the “Add…” button and it should be clear how to install the “oxt” extension package you downloaded.

  4. Shutdown then restart LibreOffice Writer.

Thanks for your help. I have successfully installed the dictionary I want now.