When I visit the ICO site I also get a "civicCookieControl" cookie which you don't list. I guess that this is probably coming from javascript and your site isn't processing this?

It's running a headless browser with JS enabled so it should be there... not sure why it doesn't pick it up. Thanks for the mention :-)

If you are running PhantomJs, did you encounter any issues like memory leaks and socket errors ?

I'd be interested in the solutions you used to solve issues like that if it's not proprietary / private.

Also interested, I've tried similar things with watir webdriver and a xvfb/headless mode but the only real 'solutions' I've come across are time-outs. Needless to say it could've been heaps better.

I didn't do much testing since PhantomJS 2.0 but I know that in the past, it was recommended to reload PhantomJS every +/- 50 pages to free the leaked memory.

We're running HTMLUnit [1]

[1] http://htmlunit.sourceforge.net/

It could also be that the cookies handed out vary geographically, or if a page includes adverts in iframes via an ad provider network the cookies you get will depend which member of the network your request is redirected to this time.

humorously, checking the site itself seems to trip it up: http://www.cookie-checker.com/check-cookies.php?url=cookie-c...

that's a feature ;-)