Hi Sophie
Others have answered the very straighforward employment points (i.e. same as being employed at M&S with employer responsible for paying you; deducting Income Tax and NI etc; providing you with a pay slip). If they don't already, is a great company called (iirc) 'NannyTax' that they can outsource that too. If they are NOT going to be taxing you at source, then you will have a major problem (as will they!) so you need to ensure you are NOT paid cash in hand.
All of that said though, THIS to me is the - faintly alarming if honest - question that leaps out from one of your posts:
'I have not started working for the family yet, we have spoken over the phone, briefly met the family to pass on my CV and CRB and I am meeting them again next week to discuss the position. I will be starting full time in July.'
If all they have done/you have done is 'briefly met', how on earth have they hired you? Equally, that doesn't stack up with 'meeting again next week to discuss the position' - is that meeting actually a further interview? Or is it genuinely to fill you in on your job requirements?
Having both been a nanny, and then employed nannies to look after my DCs, in a million years would I ever hire someone I'd 'briefly met'
Ditto, whilst I know jobs are scarce, I couldn't concieve of working for a family that, again, I had 'briefly met'.
Both as employee and employer (ESP. the latter), always interviewed at least twice and then had a 'dry-run' of with DCs and checking 'fit' was right - as if it isn't (DCs aside
) you could be in for a very long year...