lunavix, Home Childcarers are now phased out. It has been replaced by Approved Childcarers.
An Approved Childcarer cares for children in the child's home. Approval is via the Childcare Approval Scheme which does not do as much checks as would be done on a Registered Childminder, but does at least make sure the person has an Enhanced CRB Disclosure and First Aid training.
Nannies are being encouraged to join the scheme as parents using an Approved Childcarer can get some tax benefits by using Childcare Vouchers.
With regard to this specific situation, any care at your home is unregulated. In England, care provided at someone else's home (Childminder) or a childcare establishment (Nursery, Pre-School, Holiday-Club) is regulated by Ofsted, as long as care is proivided for 2+ hours - any care provider working less than 2 hours, is unregulated.
As mentioned by others, if you employ the ex-Childminder to care for your child, at your home, they would be classed as a Nanny for tax purposes - so you would need to register as an employer.