Benwen sorry I've only just spotted this as I've been away.
Take a look at my blog, link in my signiture I've got a section on interviews for UK nurses
For band 7 think about things like improving quality on the ward, how would you do it. In Wales there are the fundimemtals of care, England I think has the Essence of care. Look at the high impact changes in the NHS document as well.
Think about HR issues, dealing with poor performance ( know your policies so capabity, sickness and disciplinary)
Think about budget managment in the current climate you may be asked how you can help
with cost reduction programs so have a think about role assessments, would you rehire a 6 when a 5 could do but making sure patient care isn't affected.
Think about the safer patient initiatives and is there anything going on in the area you can progress
Motivation and retention of your exsisting workforce, how would you support the staff you have.
Making difficult and unpopular desicions as your going from clinician to manager
clinical leadership, how would you provide good strong leadership in this current climate of budget cuts and instability