Not sure I follow your argument - Pensions are not the best form of tax free long term saving IF you have already chucked in as much as you can to your pension pot ?
This spreadsheet is well worth downloading; http://www.locostfireblade.co.uk/spreadsheet/Index.html
as discussed on moneysavingexpert.com here http://forums.moneysavingexpert.com/showthread.php?t=1157173
Input the key information and you will be able to see on a month by month basis, how much...