It does not make sense to me.
CM phoned yesterday to say that a spot check by Ofsted revealed that she was over numbers so her registration has been suspended pending the investigation.
So when was she suspended - yesterday, the day before? How come you haven't had notification from Ofsted?
DH and I need to have a long think about whether we want DS to go back to her
Why would you need to have a long think about it, if you consider her to be innocent? As a user of her service you have been quite happy until now... the regulator can make mistakes... so surely you view your CM as being innocent, until proved otherwise? Or is there more to it? Have there been past issues?
I have rung Ofsted again - just for general info - and they have said that there is NO suspension on her registration.
Yet it supposedly happened yesterday (or before)... so Ofsted's computer system would be flagging it today. Also you haven't had any official notification from Ofsted... such as a letter.
It's not because she doesn't want to look after DS - she has clearly said that she intends to set up as a nanny (working from someone else's home) until the investigation is over and that she would like to care for DS from there.
When did she say that... also are you aware of how that changes your relationship - a nanny is usually an Employee, whereas a childminder is Self-Employed. A nanny share between two families is possible... but the two families need to know each other and agree contracts with each other and the nanny. Your Childminder can't care for more than two families at the same time as a nanny (of which the home must belong to one of the families) - otherwise they would be a childminder again under English childcare legislation (Childcare Act 2006).
Have you spoken with the CM about this today? Ask them for the Childcare Inspectors Name and phone number (if they have it). If they don't have the number, you can phone Ofsted's helpline and request that a message is passed on to the inspector as a matter of urgency and request that the inspector calls you.
I am agreeing with the others that it sounds as though you are not being told everything. I feel you really need to speak with your CM and get to the bottom of things.
Meanwhile, look around for alternative care. Contact your local Families Information Service for a list of childminders, nurseries, registered nannies etc.