I think the short answer is you define a role exactly how the owner/manager of the role wants to define it within any Corporate guidelines and policies. there is no external code in the UK (unlike in some countries) that specifies what should / shouldn't be in any role.

Generally most organisations probably wouldn't have those tasks being undertaken by an HR Admin, but they could be by a HR Adviser or a HR BP etc. Depending on level and structure.

The key is probably why you are asking. If its because you are being asked to undertake some of them then I would grab the opportunity with both hands. The title and recognition will catch up later but the experience will be priceless.

In reply to Keith:

Hi Keith
Many thanks for your answer. Very helpful.
Lisa