That sounds about right. £12,570 - £799 = £11,771 divided by 52 multiplied by 4 would be £905 four weekly (or just divide £11,771 by 13).
Assuming your total income is already more than £12,570 pa and no more than £50,270 pa, whatever increases you get in State Pension and occupational pension(s), you will pay 20% tax on those increases.
Hysteroscopy using spinal block/epidural


