laughingeyes, the NSPCC actually says this:
What the law says
The law does not set a minimum age at which children can be left alone. However, it is an offence to leave a child alone when doing so puts him or her at risk.
How to decide if you can safely leave a child alone
There are many important things to consider before you decide to leave a child alone. These include:
the age of the child
the child's level of maturity and understanding
the place where the child will be left
how long and how often the child will be left alone
whether or not there are any other children with the child.
For example, most parents would think it is okay to leave a 16-year-old alone for the evening. But to leave them for a week would be unacceptable.
Many young children play outdoors with other children without supervision, most people would agree that this is an important part of growing up. To leave children outdoors for a considerable length of time though, or to allow them to wander off without knowing where they are going, would be unacceptable.
You are the best judge of your child's level of maturity and responsibility.
I suggest if you want accurate information from the NATIONAL SOCIETY FOR THE PREVENTION OF CRUELTY TO CHILDREN, you go directly to the NSPCC website rather than that of East Sussex Council. It's here.
www.nspcc.org.uk/help-and-advice/for-parents/keeping-your-child-safe/being-home-alone/home-alone_wda96754.html#decide
Incidentally, I leave my seven-year-old for short periods while I go and pick my youngest up. He knows my mobile number off by heart, has never set the house on fire and knows to ring his dad if I don't arrive back within a certain time (so is unlikely to STARVE TO DEATH if a HELICOPTER CRASHES ON MY CAR, or whatever else people think will happen.)
I do this because I know my child and his level of maturing and understanding and because I am capable of evaluating risk.