www.bbc.co.uk loaded for me instantly on Safari (and I use AEBS as router with the firewalls turned on except for file sharing for my LAN).
7 weeks ago I had major performance issues with Safari and the iMac in general. Everything is running optimally now but it wasn't easy.
Try emptying the Java caches - go to Applications/Utilities/Java - click on both 1.3._ and 1.4._ and follow the tabs and buttons to clear the caches.
If this just started happening 3 days before your post as opposed to a general slowdown and preformance problem over time, then as Bee mentioned, it seems as if something was added that precipitated the problem in your case - perhaps a 3rd party application was installed or one of the security or software updates from Apple?
Is this happening just in your User account or is it the same speed problem for all of the Users on the computer?
(I have some other suggestions
here.)