1—’I just read about the principle of parliamentary sovereignty in UK. Does that mean that Parliament is unanswerable?’
In theory, yes. Although many would argue not actually.
http://en.wikipedia.org/wiki/Parliamentary_sovereignty#United_Kingdom
http://en.wikipedia.org/wiki/Parliamentary_sovereignty_in_the_United_Kingdom
http://www.parliament.uk/about/how/sovereignty/
http://www.theguardian.com/law/2011/jan/27/supreme-court-parliamentary-sovereignty
2—Police can only enter premises without a warrant if a serious or dangerous incident has taken place. There seems outside the UK to be some confusion with the ‘warrant card’ all British police carry:
http://www.yourrights.org.uk/yourrights/the-rights-of-suspects/police-powers-to-search-premises/
http://www.findlaw.co.uk/law/criminal/your_rights/500466.html
http://en.wikipedia.org/wiki/Warrant_card
So, a warrant card is simply a police officer’s ID & proof of rank/authorized powers.
Not the fabled “pocket warrant” that some Yanks believe makes judges unnecessary when police are searching homes.
Back to topic: were Geller & Spencer denied entry to UK because their views were deemed innately offensive, or did the Home Office fear Muslim riots were they to speak?
Maybe they remember how Lord Achmed buffaloed the House of Lords over the “Fitna” video. Threatened to surround Parliament with 10,000 angry Muslim men if it aired in chambers (sorry, couldn’t resist).