publications.education.gov.uk/eOrderingDownload/DFES-0025-2002.pdf
I came across this when looking for legal guidance on what lea's resposibilities are for education of a child unable to attend school because of impact of medical needs.
It includes:
"leas should ensure that:- pupils receive an education of similar quality to that available in school, including a broad and balanced curriculum"
- pupils educated at home receive a minimum of 5 hours teaching per week. This is a minimum and should be increased where necessary to enable a pupil to keep up with their studies"
Strangely 
our lea only appear to have heard of the minimum 5 hours per week bit.