Software4Students have Office 2008 currently listed at £38.06.
Microsoft are currently offering a free upgrade to Office 2011 on any valid purchase of Office 2008; see link below:http://www.microsoft.com/uk/mac/products/Office2008/office-2011-upgrade.mspx
This means you can get (when available) Office 2011 for just £38.06! As long as you buy Office 2008 between Aug. 1, 2010, and Nov. 30, 2010.
If you are not eligible for the student offer, then the same deal from Microsoft applies from other stores.
Note: There is a compulsory transaction charge of £1.95, making the total £40.01.