Good grief...if ever there was need for a definition of full-time, you could successfully go by the hours it takes to keep up with DfES-initiated Consultation Processes.
So yes, you guessed it...there is yet another consultation up at the DfES, this time looking at defining the notion of "full time education". The nominal intention behind this one is to bring small educational institutions which take children in on a more casual basis back into the grasp of OFSTED. So yes, some home educators could be affected in that quite a few of us have looked to leave our children in informal school-type settings, though experience with such ideas round this way suggests that these ideas fizzle out quickly at the prospect of government intrusion.
Whilst it doesn't look as if the primary purpose of the consultation is to take home educators to task for not obviously schooling their kids for a set number of hours, I sure think we should keep an eye on this in order to ensure that it doesn't sneak by us.