I talked with him just now. I showed him this picture, and he said "yea, thats it". 1952 model. I wrote down the MXX231 number and told him to see if thats whats on it. He says he has the title for it, and it "starts and runs" but that was likely 20-30 years ago.
He also said he once had a 3rd bus but sold it years ago.
I asked him if he would be interested in selling it, as I've had a few inquiries over the years about it, and he said he would. I told him I could come over and photograph it for him. So, if anyone out there is SERIOUS about purchasing this bus, get with me. May or may not be the MXX231, but its definitely a 50's British double decker bus that may be in running condition.