If I go to www.booker.co.uk it starts to open http://www.booker.co.uk/home.aspx, then hangs, saying it is downloading some .png file. I can't open any of the links on that page either.

If I go to www.sainsbury.co.uk it readdresses itself to http://www.sainsburys.co.uk/sol/index.jsp and just hangs

I have Norton Internet Security. There is no "blocked cookies" showing, and both sites are in the "Internet" zone, no blocked site indicator.

I can open the sites on my phone so I am confident it isn't at their end.

What should I look for?

I tried Internet Explorer with Add-ons disabled, and it then works.

But this is rather tiresome.

They both work on my pootah. Browser issue??

Both work here as well.

Try deleting browser cache files and try again.