Answer to Question 2:

Dear John,

If an employee is off duty, as a result of injury or illness, they should not recommence any work (overtime or regular hours) without being declared fit for the work they carry out by your occupational health doctor or their own G.P. Your employee should provide you with a fitness to work medical cert so you can be made aware of (1) whether your employee is fit to carry out their duties or (2) of any particular requirements they may need to carry out duties (e.g.) specific risk assessments , such as detailed manual handling assessment, VDU assessment, or re-training on machine/equipment, or (3) any recommendations the medical people have (e.g.) reduced hours for a couple of weeks, more frequent rest breaks etc to facilitate recovery and rehabilitation for work.

Not ensuring the employee is fit for work before 'calling him in' does not demonstrate due care for employee or any member of the team he/she works with.

You should contact your HR department re: payment query. 

Hope this helps.
Paul