Worked for Capita IT services (as a software developer), left 18 months ago. Good people actually doing the work, but everything else about the place was awful. No career progression, no rewards for working hard, no reviews, no staff development, no pay rises, bizarre corporate rules, in-fighting, etc.
Senior management seemed to reward themselves for screwing up projects and alienating staff. Anything that got delivered was done so despite the management, not because of it.
No idea about the other companies but in my experience Capita is a soul destroying place to work