Hi velvetkatze
Welcome to BrillKids
If you decide to use the BrillKid program you can purchase with the option of US or UK English.
Have you tried the free 2 week trial?
You can search the forum by clicking the search tab above and typing Japanese to see any related posts.
If you decide to purchase BrillKids there are 39 Japanese files you can upload into your program.
You also might find some useful info on products by going through the posts on this link
http://forum.brillkids.com/product-discussions-and-reviews/Hopefully someone else can share what other programs besides BrillKids that offers UK English
With the help of everyone on the forum here I have been successful in teaching my son languages I doubt I will ever master.