My 3 year old DS attends pre-school, has done since he was one. He is entitled to the "30 free hours". He attends 3 days a week, from around 8.45 til 5.30, so taking that as being billed 8-6, it is literally 30 hours per week.
My bill this month was £389.70, reduced to £292.27 after the 25% tax free element which we use. We can afford it and our childcare bill is SO much less than it used to be when we had two in nursery/pre-school, with limited entitled to "free" hours.
But I really think the title of "30 free hours" is ridiculous, when my DS attends for 30 hours and the bill is still nearly £300 per month.