Yes, the guidance is the form of the role maps and NOS. The relevant unit being WM7 - that people should recive development is clear through IPDs - examples:
All development is intended to be personal and role specific and will be identified through the Personal Development Review Process. Everyone has responsibility to look after their own CPD and at every level in the FRS skills like leadership and communication are important and should be developed within the workplace
http://www.ipds.co.uk/public/site/newsdocs57/helix%20explained.pdf shows the route to the next level.
Assessment of competence will be by experienced supervisors, if the NVQ process is being applied then they must be qualified. Everyone's competence is now constnatly monitored (or should be) as IPDs requires that maintenance of skills be adopted and recorded
I suggest that FRAs that are not using these natioanl policies and guidlines should be giving good reasons why not.
Before you can act-up or be temporary you need to satisy this (s20 Pay of Grey Book):
20. It is necessary for an employee who acts up or is temporarily promoted to have:
(1) demonstrated competence in his or her current role;
(2) demonstrated the potential to develop beyond his or her current role; and
(3) successfully completed the relevant assessment process for the higher role