I am a native English speaker applying for teaching positions at various language schools in Kraków - what is the going 'hourly' (i.e. 45 minute) rate here for native speakers?
It depends, but the best piece of advice is to look at the amount of work needed to work one 'clock' hour - if they expect constant lesson plans handed in and expects you to attend constant professional development courses, then ask for considerably more than you would from a school that's happy for you to turn up and do what you want.
Also, tailor it according to what they want - if they want you to work awkward split shifts, then of course, raise the amount requested.
What money you get - well, it's up to you to negotiate this. Many people will share stories of how they get 60-70zl net an hour from schools, but I don't believe the vast majority of stories. Realistically, you should aim for 35zl net minimum from a 'method' school and at least 45zl net from a 'traditional' school - to reflect the workload. Don't be so quick to discount such 'method' schools though - financially, it may work out much better to work 25 hours in a 'method' school with no preparation versus 25 hours in a 'traditional' school that requires oodles of preparation and leaves you no time for the private lessons.