Just in case your not aware skype is now free on three. No monthly top up nothing. So for the price of the phone to be charged every other day or so. The Wife has free skype calls anywhere she can get a 3 mobile signal.
Also you can send off for free PAYG sim cards so if you have an old 3 phone skype capable mobile sitting in a cupboard etc. You maybe lucky
Im also looking in to where it says which 3 mobiles come with skype on 3 it offers you the chance to download a link for some models. As three have a statment on their site saying soon many 3g enabled unlocked non 3 phones will soon be able to use the service.
Warning not all phones are able to use this service and i strongly advise you read though the website and check and then double check.
http://www.three.co.uk/Mobiles/3_Skypephone
You can both skype message and talk.
The old cost used to be on PAYG 10 pounds a month to give you access to the skype option so a saving of120 pounds is possible. Of course it means the mobile can not be used for normal calls, sms etc you would need to load some credit on.