After reading this article: Globalization, Mirroring, Dynamic Functions and Properties in EPiServer Composer 4 R2 and the Composer documentation I realised there was an eay way to Translate an existing web page that has many Composer blocks.
The way was to open the non-translated page in the CMS > Edit > Click Versions on the Toolbox > select different language from drop down and click copy. You need to wait a few minutes, but on the version I have (R2) I get a 400 ERROR.
We currently have our site on a 4 server farm and I was wondering if this was the issue.
Does anyone know how to fix a 400 ERROR when trying to translate a webpage using the CMS / Composer Toolbox?