Life-Like Hobby Kits did a series of reboxing of old Revell (I think) kits. One of them was the State Coach of England and came complete with Queen Elizabeth and Prince Phillip. It was around 1/48 scale, maybe 1/40 scale. I listed it on eBay a couple years ago, but I do not believe it sold. I think it went back into the basement stash.
Here is a photo of one I found on eBay, not mine, but mine was just like it.
Edit: yes, I looked it up in my Remembering Revell book, released first in 1953 and several times in the 1950s (with and without horses) and is listed as 1/48 scale. It was originally a Revell kit.