how can I download a GB version

Every time I install version 6.4 I get a US version, even after selecting English GB from the list of languages

What is your operating system set for?
US? GB?

What settings have in USER INTERFACE and LANGUAGE SETTINGS? If you are using Linux you will need to download the ENGLISH - UK Language pack.

Thanks for all your comments. I use Windows 10 and in fact not all my language settings were correct. I had to change my hard disc last year and when reloading the operating system it possibly reverted to some factory default settings. However even with all the regional and language settings now correct, Libre Office still won’t load in UK English. The User Interface and Locale settings are UK, but the default language for new documents is always USA. In theory you can change this from Tools, Options, Language settings but it only works for the current document and reverts to USA for the next document. I have tried Custom installation but as far as I can see this only allows specification of a completely different language, not different versions of the same language. I never had this problem with version 5 of Libre office so I think it must just be a bug in version 6.

Have you checked that your Templates that you are using and the Paragraph and Character styles are correctly set to use English UK?

Thanks. To be honest I have never understood how templates and styles work in LO, but with the new built-in help I will have another go. If you could create a default template with UK English in it, that would solve the problem. For the moment I have solved it in another way. My old documents, created in LO version 5, have retained default language UK English. So I have taken one of them, deleted all the text in it, and re-saved it with the name New Document. If I use this for typing all new documents then they will all spell-check correctly.

taken one of them, deleted all the text in it, and re-saved it with the name New Document

When file associations are properly set, you can simply right-click on the file in Explorer and choose New… from the context menu. Or, for true machos, use the command line as follows:

<full path to LibreOffice executable> -n <full path to the document to be used as a template>