The general rule used to be salaries/pensions etc could be discussed at 2nd interviews.
If you go through a recruitment consultant then , once the offer is made you can let the recruitment consultant do the haggling. They do it day in and day out and as their commission is based on getting you a good deal they tend to do a good job.
That said, getting to and from job interviews can be expensive. I think there is no harm in asking for the range of salaries on offer even if they won't tell you the specifics.