I'm a HCA. At my interview I was asked how I felt about handling wee, poo etc. (obviously a big part of the job - the answer they are looking for is 'That's not at all a problem for me').
They might ask you how you feel about doing shifts if the job involves shiftwork.
I think I also got asked about teamwork e.g. what makes a team work well together.
A big thing in the NHS is working within your limitations i.e. not doing things you've not been trained to do, so they will probably ask you a question to figure out if that's what you'll do (if you have any doubts about whether or not you should be doing something you go to the nurse in charge).
Try and mention in your answers that you'll stick to infection control and manual handling policies, and promote patient dignity - that's another massive thing (basically empathise with the patient. Do they want the whole ward to see them being hoisted onto the commode? No, pull the curtain. Etc.).
And I got asked how I'd deal with a patient dying. Obviously you'll have patients that die and you may be asked to help lay them out when they do (I've been a HCA for two and a half years and haven't yet had to do this, but I only work part-time). I said I was confident I could handle it but if I found myself struggling I'd get in touch with either the hospital chaplain or the staff counselling service (find out if your trust has such a service).
You will almost certainly be asked about confidentiality too. For an idea of what to talk about, google the Caldicott Principles - these are what all NHS confidentiality policies are based on. The only time you'd break confidentiality is if the patient indicates they are harming themselves or other people.
Hope that helps, do come back and tell us whether or not you are successful.