Well relatively cheap (if you are making a lot of calls)....
I was finding that ringing Poland on my mobile was costing me £10 for seven minutes. What i have now is a Skype To Go number. I have been allocated a UK phone number which i can phone and it connects me to my beloved in Poland.
I use it to call Prague from the UK, costs a couple of pence a minute, or free if both you and the person you are calling are registered.
Just checked out rates if calling from UK to Poland:
JAJAH Rates*
From landline: 2 pence to landline or FREE between Jajah Users. 10.5 pence to mobile phone or FREE between Jajah Users. From mobile phone: 9.7 pence to landline or FREE between Jajah Users. 18.2 pence to mobile phone or FREE between Jajah Users.
* Applicable rates are displayed during the call and may vary depending on the operator. For users from the EU: all prices are listed without 15% VAT. As of May 1st 2007, free calls are only available from JAJAH Web. (Jajah cheap rates still apply to all calls initiated from JAJAH Mobile Web and from JAJAH Mobile Plug-in).
I would check this out thoroughly though because all I know is it worked for calling my folks! I don't really know anything else about the company or even fully understand how it all works!!