I know about kinship care from a social work perspective Waspy. As nellie says, a crucial point is whether or not children's services were involved in placing your granddaughter with you. If they were, or if there were concerns that meant your granddaughter might have had to be taken into care if you hadn't stepped in, you are entitled to a full package of support from them. If they weren't and this is a completely private arrangement, then you have fewer rights.
The kinshipcarers.co.uk website is a good one, and through it you may have found your way to grandparents plus (if you weren't already aware of this) which is an organisation that can offer support and legal advice.
www.grandparentsplus.org.uk
There are others on here who have a lot of experience from your side of the fence and who have had to negotiate the complex systems for themselves. I hope someone with that knowledge will come along soon to give you their perspective.