More pictures here:

https://www.shutterstock.com/editorial/search/london-to-calc...

There are photos in the article references! I didn't find one of the kitchen.

https://curlytales.com/this-was-the-worlds-longest-bus-route... https://www.techtraveleat.com/story-of-london-culcutta-bus-s...

Exactly. I really wanted to see what a bus with sleepers for everyone, a full kitchen and restrooms looked like. It couldn’t possibly have fit that many passengers.

Edit: I found pictures. It was a double decker.