And can there really be too many days off as if someone sick there sick and there nothing anyone can do about it
Depends on the context, they certainly shouldn't be blindly issuing warnings because the Bradford factor gives a score of X.
If someone has a chronic condition that might mean several short periods of time off or maybe a mix of taking half a day off and working form home etc.. then that context ought to be considered rather than blindly applying some formula. If they don't then I suspect that a good employment lawyer can cite his client's disability and tear them a new one if it becomes a serious issue. It doesn't make someone immune from being fired though, I guess the employer needs to take a more holistic approach, see what value they're getting form the employee and if he/she is still meeting deadlines, getting **** done then it shouldn't really matter if they take a day or half day off quite frequently or frequently need to work from home etc.. so long as they're delivering.
Obviously if someone who doesn't have a chronic condition or similar reasonable explanation keeps on phoning up on Mondays during the summer or after bank holiday weekends with "I've got a bit of flu *cough* *cough*" then that is perhaps another matter and could certainly be something HR might want to have a word about.