Latest on this, I asked SWSoft Support if they could possibly change the language selection to read just 'English' instead of English (United States) they came back to me saying the could NOT do this, although I feel sure they could.
On creation of language packs, apparently there is a tool scheduled for release in February to do this, I'd really like something much sooner and it's likely February could turn into sometime later in the year. I emailed the department involved in with language packs again, asking for a list of all files in the language packs, so I could pull copies of the U.S. files from my server and start converting to English (British) but I haven't heard anything further back from them.
It might be a worthwhile exercise for everyone to contact SWSoft support and express their interest/ request for a British language option, or at least to change the language selection to read just 'English' instead of English (United States) as a temporary solution.