PF and variable rate application providers

Hi everyone.
I'm working on a project regarding variable rate application, specifically of nitrogen fertiliser, and I am looking for companies offering this kind of services. Can you help me telling me about companies in the UK offering PF services in general and VRA in particular? I would appreciate your help.
So far these are the ones I've found
SOYL
Courtyard/IPF
Agrii
Hutchinsons/Farmacy
Bayer Crop Science
Soil essentials
Agrovista
ADAS

Many thanks.