'First, I'm going to mention that 14 of the 20 highest tax rates in the world are OECD, so excluding the data to include only OECD is going to make the UK's tax rates look lower than they actually are.' -
In fairness, You can't really group nations with massively divergent economies together and get any meaningful comparison. Generally the OECD have all got developed economies which makes taking them together more useful.

The world average is rather meaningless in that sense.

That said, your updated data is good, but it still doesn't convince me. Also, you're being disingenuous - 1995, UK is 0.3% below the average, 2000: 1% above, 2004: 0.2% above, 2005 0.5% above, 2006 1.2% above - it has been holding steady over that period around the average.

Making a world comparison, it is true that this average may be high, but it is the 34 most developed countries. So what if they all have high taxation compared with developing countries? That is a very different claim than the UK has some of the highest tax rates in the world.

Infact, it is more interesting to note that the US seems to pay on average 7% less than the rest of the developed world. (perhaps this can account for lower standards of education and life expectancy - see: https://www.google.co.uk/publicdata/explore?ds=d5bncppjof8f9_&met_y=sp_dyn_le00_in&hl=en&dl=en&idim=country:USA:GBR:CAN )