I received the following reply from Colin Young at Royal Mail today. A sterling service all round:

Dear Mr Young

Thank you for your request for information received 1 November 2005. You
requested the cost of a 1st class stamp.

1st class post costs just 30p for sending inland letters and packages
weighing up to 60g. Further details of Postal Prices for first class and
other services can be found on our website using the links below.

First Class:
http://www.royalmail.com/portal/rm/jump2?catId=400028&mediaId=400029&_requestid=82630

Other Postal Prices:
http://www.royalmail.com/portal/rm/content1?catId=400023&mediaId=9300094

If you have any queries or concerns please let me know.

Yours sincerely

Colin Young
Freedom of Information Unit
Company Secretary's Office
foi@royalmail.com

Royal Mail is a trading name of Royal Mail Group plc. Registered in England
and Wales.
Registered number 4138203. Registered office at 148 Old Street, LONDON EC1V
9HQ