Family member got promoted to 5-month senior post but then had transplant

Andy_L

Their rights are to their contractual sick pay. That could be based on any of:
1. the higher rate of the senior role
2. their average salary over the last, say, 12 months
3. the rate for their previous post because the terms of the 5 month senior post specifically exclude using the salary for any other benefits 

As far as keeping the higher post it depends on the terms of the appointment

bottom line - only the employer/staff handbook/Contract can answer the question