In a bid to counteract Vonage's unlimited offers, Skype is offering 180-days unlimited free calls to UK Landlines to anyone who buys £10 Skype credits. There are no limits to the duration of the calls and as long as they start with 01 or 02, you should be safe.
Broadband users can expect to slash their phone costs if they switch to Skype. The Skype user can purchase Skype Credit through the website (using PayPal or a UK-issued credit/debit card with a UK billing address) or Skype e-voucher purchased at Sainsbury’s supermarkets.
Unfortunately, the promotion is not applicable to call forwarding. While you can forward calls you receive via your Skype Name or SkypeIn number to a UK phone number, these will be charged at standard SkypeOut rates. For more information, check this page.