Hello, I'm Keith and happy to help you with your question.
Assuming that your wife will be on GBP 8-43/hour for a 24 hour week then her anticipated monthly income would be rate x time x 52 / 12 which equates to some GBP 877 per month. Take her coding which represents a monthly personal allowance of 833 leaves her with 43 quid per month to be subject to tax at 20% = about 9 pounds. What will happen in due course as the new hours kick in and the salary adjusts downwards is that the tax tables will take this into account and make the necessary adjustments to bring her tax neutral by the end of the tax year. I have ignored the pension contribution which may well reduce this even further. Without a full knowledge of the pension scheme, often hideously complicated, I cannot include the deduction in my summary computation. NI deductions I would estimate to be of the order of GBP 11 per week, say 50 quid a month.
I do hope I have thrown some light on your wife's situation.