A BBC Witness History video on Mary Coombs, who “worked on the first LEO computer and was the first woman to become a commercial computer programmer.”
The video gives a brief look at the LEO in action as well as her life while working on the computer.
Wonderful!
There’s an excellent book, A Computer Called Leo, by Georgina Ferry:
And I see there’s a preservation society, credited in the video:
The LEO Computers Society (which has charitable status) started life as a reunion society for people who worked on these remarkable machines. Its principal mission now is to ensure that LEO’s heritage is preserved, protected and - importantly - promoted to wider audiences.
Edit: and a mini-site at the CCH is also associated with the society:
Welcome to LEO, the first business computer
When computing was a piece of cake, literally… 
Here’s a new 30 min documentary with some first person accounts and some historical images:
(It’s from the Centre for Computing History, in Cambridge.)
Once LEO was in operation and became known about, other people came to the Lyons management and asked can we use your computer?
And this included, for example, the Met Office. It included the people who were building military aircraft and they came to us, can we do that?And we programmed that for him, and it became a regular weekly job in an entirely new way.
For the Ordnance Board, LEO worked out range tables. For Handley Page, LEO carried out flutter and stress calculations for faster, safer flight. For Attwood Statistics, LEO analyses the findings of market research.
For the coal board, LEO worked out the classifications in the fight against pneumoconiosis.
For the British Transport Commission, LEO worked out the shortest distance by rail from each station to all the other four thousand.
This would have taken fifty clerks five years.