Phone up and complain. You should not have been charged extra tax on top.
I did some Googling, and found someone charged 23% tax by MS for Office, because of being outside Ireland but in the EU:
http://www.microsoft.com/en-cb/offic...D0EBAAAACAAAAA
Your case *must* be a screw-up on the part of MS.
I *only* paid £59.99, via the phone (as the website refused to work).
There is no mention on the website of the price being £59.99 excluding VAT / sales tax, and no mention in the policy terms of the price quoted not including tax.