Associate Acronyms with their definition

[AlainVagner]

In the preface, you use some acronyms like ONS, RAP, PI, etc. The text could be easier to read if they would be associated with their definition, at least for their first appearance, ex: Office for National Statistics (ONS).
Some of them are not defined, ex: Principal Investigator (PI). I don't know if this is so well known outside of R&D circles.

[b-rodrigues]

That is a very good point, I will go through them all!