Try heat. On the caliper itself at the back of where the pins insert, that should expand the hole. But even heat direct on the pins might do it, might break the corrosion seal. When they're hot try getting a punch on the end and bang them in a bit more - I know it sounds Irish but the impact will break the corrosion and you can then wiggle them out with some grips.
Coppaslip when re-assembling, obviously
