Shane, thanks for your help.
Yes, I have I have disabled all add-ons, and checked they are all disabled for Toolbars and Extensions, Search Providers, Accelerators and Tracking Protection.
In fact, I have run the Fixit at 
http://support.microsoft.com/mats/ie_performance_and_safety which it says fixes:
•   Defective Internet Explorer add-ons. Disables defective add-ons.
•   Phishing filter is turned off. Turns the phishing filter on.
•   Pop-up blocker is turned off. Turns the Pop-up blocker on to block pop-ups.
•   Security settings are not set to recommended settings. Resets security to recommended settings.
•   Internet Explore does not update cached pages or updates them inefficiently, causing launch to be slow. Resets the page sync policy to automatic.
•   Cache size is too small or too big, causing slow performance. Resets the cache size to be within 50-250 MB of the default range.
•   Concurrent server connections set too low or too high causing slow performance. Restore IE concurrent connection settings to defaults.
•   Pop-up blocker is turned off allowing pop screens. Turns the Pop Up Blocker on.
•   Resets Internet Explorer security settings to the default (recommended) levels.
•   Enable the Phishing Filter.
•   Enable Data Execution Prevention for Internet Explorer
I have also tried IE with Advanced/Setting  ‘Use software rendering instead of GPU rendering’ ticked and unticked, and a bunch of other stuff I gleaned from the net.
I should have mentioned, in case it matters, that my PC is running the 64-bit version of Windows 7 SP 1.
I have, since writing my email, been searching yet more on the net and wonder if there is a corruption in my Registry and if I should be re-registering IE dll’s.  From reading MSDN Internet Explorer Architecture  
http://msdn.microsoft.com/en-us/library/aa741312(v=vs.85).aspx a key dll seems to be mshtml.dll which ‘renders’ html (I assume this means displays it on the screen).  Should I be re-registering this by running:
regsvr32 mshtml.dll
Am I right, and if so what other dll’s should I try to re-register?
John