In fairness to Google, they are only doing what any thinking company or person would do... They are looking for ways, within the law, to minimise the tax that they pay. Many of us do exactly that, for example balancing pension contributions/withdrawals, or even charitable donations, etc, against tax.
The real fault lies with governments that set the legislation, that leaves gaping loopholes open. But even that's not so easy, as closing loopholes encourages Google and the likes to base themselves elsewhere, a big loss to the economy.
If they came clean and said "Yeah we've hired skilful lawyers and they've found an angle and beat the UK system", then I would begrudgingly respect them, and respect their lawyers too. But it is the pretence of 'decency' that bugs me, especially when the Google spokesman just can't stop smirking.