That's a tricky one although I would feel the same.  Maybe they want the accountant to hear!

Is there a ballpark figure that has already been mentioned?  Do the panel already know the currently salary or level you are at?  Did you mention it at the previous interview or on your application form?  Most interview panels will have already gauged an idea of your level and currently salary even if you haven't disclosed it.

I suggest you run with the second interview and see how it pans out.  Salary is sometimes not discussed until an offer is made, although at this level, we usually know what we are looking for that is going to make a move worthwhile.

Obviously you want to better yourself and negotiate a higher salary than you are on at present but you should always wait for the panel to mention salary, never raise it yourself.  A simple way of indicating a figure is by saying, "I would be looking for something in the region of £xxxx on top of my current salary".  You could always ask for a pen and paper to write it down if you felt it was impossible to say.