Also need to look at the Tax haven's of the rich and greedy corporates too like Luxemburg etc...

http://www.bbc.co.uk/news/business-17993945

Glaxo SmithKline mentioned, but many a global company Headquartered their for no reason other than Tax avaoidance.

Amazon comes to mind

http://www.guardian.co.uk/technology/2012/apr/04/amazon-british-operation-corporation-tax

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and others effectively weilding drawn out legal proceedings to basically avoid tax - Vodafone (large stakeholder in Verizon Wireless)
http://www.guardian.co.uk/money/2011/dec/06/hmrc-tax-deal-vodafone