Hi rickman - I'm vice-chair of my local Home-Start, so perhaps I'm biased - but I think they're great (I know ours is).
The volunteer will work within strict confidentiality guidelines - there are some very obvious limitations to these guidelines - which she should explain to you. She should not be there to do things for you, but to give you support so that you can do things for yourself (with her support). She might be able to advice re; carer & toddler, or other support groups, etc / might encourage you to take the kids to the park, etc (with her). She should be carefully matched to your 'need' - and might have similar experiences to yourself (if you're lucky). Home-Start volunteers are very well-trained, and have to have experience of being a parent themselves.
Some of the information on the links that have been given below is wrong. For example;
I'm concerned about the volunteer who took the child out whilst the mother cleaned ...a volunteer (or a paid worker) should not take your kids anywhere without you - this is definately against policy and practice. HS VOlunteers are not trained as childminders...nor are they covered by insurance to look after any kids without the parent present.
Neither are they government funded - we have to fight and struggle for funding regularly and get absolutely no government money!!
PS - we offer a totally different service and focus to Sure-Start - but are compatible and often work in partnership with local Sure-Starts.