Google for Paddington by Steven Moye. A freeware package by the guy that wrote the Fontographer book.

Paddington, eh? Interesting.

Had you not said that Bojev I'd have suggested the more obvious Gill Sans as a working alternative. Eric Gill worked closely with Johnston on the Railway Type project and the later Gill Sans bears more than a passing resemblance to Johnston. Without grabbing Gill's biography I have a recollection that he worked so closely with Johnston that he drew a lot of the Railway Type designs for him. I could be wrong on that though. There are obvious differences, but in spirit it's frequently very close. Well, bar the diamond i and j dots and Gill Sans' interchangable 1I and l.

It is neither here nor there as they, Gill and Johnston, do look alike in many ways... But, IIRC from my own research on Perpetua, Eric only attended 3 meetings in the beginning of the development.

I think Johnston is much more Geometric and adheres too much to the circle for my taste.