Willy,
to fund two children at a cheap nursery(if you can find one) you need about 30k pa gross and 40k for some in FH area. If this leaves you with 5k after the childcare costs are paid. Pay tax at 22% plus 10% NI and it leaves you with 3400 net. The child benefit on two children 1700. Now, would you complain if you were loosing 30% of your income? That is the calculation someone on 45 k and 2 small kids may be loking at.