I am surprised your company wouldn't have something in place already in the form of return to work interviews and guidance from HR. Close communication between all parties is key - HR, H and S, line manager, the employee in question and other parties e.g. GP (fit note) and Occupational Health depending n illness/injury. What currently happens? Many factors to consider of course - type of illness, type of work, length of time off, re-assessment, re-training? Bringing back part -time, reduced hours is but an option to consider after a full return to work interview and an assessment as to the employee's work role capabilities - perhaps alternate work could be considered for a short period? reasonable adjustments might be able to be made in current role? Each case has to be looked at independantly in my view - yes have a procedure on the "steps" or guidance to follow but each individual case is bound to be different.

Since you ask for a HSG, the approach in HSG 48 on error management and behaviour is relevant.

If you are scientifically trained, you can also find useful guidance in the ergonomic risk management process set out clearly in the ACOP of the Management of Health and Safety at Work Regulations 1999