When you have a non polish cell phone (or British mobile) and want to call a cell number in Poland, you have to dial +48 and the cell number. Cell phone numbers are 9 digit e.g. 605-555-555 and mostly start with 5,6,7.
If you want to call a stationary phone from a non polish cell phone you have to also dial +48 (polish international code) and area code for the city you want to call f.e. (22) for Warsaw or (12) for Krakow, (ex. +48-22-420-20-20) Stationary phones have 7 digits and are shown like 420-20-20 or 012-420-20-20 with the area code.
When using a polish stationary phone or pay phone and calling local numbers, you also have to dial the local area code and the number.
To call a cell phone number in Poland from a stationary phone you must dial 0 then the cell number, f.e. 0-605-555-555.
All emergency numbers in Poland are free (112, 997,998,999).
Taxi corporations use mostly 4 digit numbers f.e. 9494. To call for a number like that from a cell phone you must dial +48, area code and the taxi number. Check your provider for rates on roaming in Poland, and know your embassy number.