I said 50% of my income is taken in tax.

Basic Rate Tax @ 20%
Higher Rate Tax @ 40% (over £34800)
National Insurance typically 11%

That's the direct taxation on income.

Then we have Council Tax, VAT, Tax on Fuel, Tax on Alcohol, Tax on Air Travel, Insurance Tax, Road Tax, Betting and Gaming Duties, Tobacco, Savings Tax.......

So work it out and 50% is about the typical tax take from an average earner.

Tax was forecast to be 37.3% of the GDP for 2008/9 but remember that the tax take is skewed because the 37.3 is not paid by everyone. The typical middle income earner is carrying proportionately more.

Of a UK adult population of around 50 million, it is estimated that there
will be 30.6 million taxpayers in 2008–09. Around 3.6 million of these will
pay tax at the higher rate, providing 55.8% of total revenue.

So if 3.6 million are accounting for 55.8% of revenue, that means that 27 million are only accounting for 44.2%.