They are employed. I spoke to an expert on this at the tax office after being passed around and the unequivocal answer was that they had to employed. The only way possible they could be classed as self employed was if they also freelanced as assistants for other childminders in the area. But as I was the one fixing hours and they were expected to work for me for those hours (if they didn't turn up because of work elsewhere I would be over my allowed adult:child ratio) they had to be employed. I have heard it said that as long as they are 'free to look for work elsewhere' they can be self employed. That is incorrect or everyone would be self employed as there's nothing stopping any employed person 'looking for work elsewhere'.
I have found my assistants from gumtree and have also used live-in assistants (gap year european students). The advantage with live-in assistants is that they are less likely to go sick, are exempt from the minimum wage (altough I do always pay the minimum wage), and are also exempy from needing an off duty meal break (this can be a problem if you still need to keep to ratios and they have to be counted out for their breaks)
A good assistant is someone who has experience with under fives, is kind with initiative and a young smiley face (the children all love a kind, lovely young face - much nicer to gaze at that mine!)
Qualifications I have learnt to my cost do not matter half so much as an intelligent eagerness to learn and intuitive way with little ones.
If the interview is hard work or all one sided don't take them on. Only take on someone wo you can genuinely feel a rapport with.
It's quite possible to give them some online training to do once you've got them on board.
I decided I needed one because I was finding the days frustrating with three babies/toddlers especially when one was very clingy and I could never feel I was doing what I really wanted to do without endless interruptions. I wanted to have a busier house with more of a small nursery feel as I think the children learn more when in a larger group but still with a one to three ratio.
Ofsted will let you have up to six under fives when working with an assistant if you have the space and can show at inspection that you are a good minder (with adequate equipment and good paperwork/policies/procedures etc). I can have two under ones when working with my assistant.
It's a big step to take but has worked very well for me and the children benefit immensely.
Send me a message if you would like copies of assistant contract and induction procedure etc