They've stopped the allowance, and a lot of deductions that they used to have (remember when we could deduct mortgage interest?). There are very few now, except for the child credit the others mentioned. I think the only one we get in addition is an allowance for professional memberships, which really doesn't make a difference.
UK Income tax:
10% for 0-2090
22%: 2091-32400
40% over 32400
NI: depends on employer, but generally 9% for the employee and the balance paid by employer.
The overall rate for us is not that different to the US, but the difference is that in the US you can deduct mortage interest, property tax, state income tax, etc, etc, etc, which (for some) brings the overall level down significantly.