just to add, in my school where I teach, all PPA is covered by level 3 TA's, this includes reception. I am not familiar with the rules for nursery classes as we do not have a nursery at my school, so cannot comment on that.
If a teacher calls in sick, for their first day of absence, the TA takes the class for the morning and the class is split for the afternoon. I also know of many other schools where friends of mine teach where this is the case. It saves money for a PPA teacher. It also allows TA's to stay with children if the teacher wants to take children out of the classroom in small groups or individually to do a task.
"However, it states that a qualified teacher with QTS must be present at all times, and some unscrupulous heads are using HLTAs to teach while the teacher does her PPA in the same room"
Actually, not true! Seperate to the PPA aspect of the above quote, my best friend who is also a Canadian trained teacher, came over here in January 2008, and has since been teaching as an "unqualified teacher" in British eyes. She teaches reception currently and in the eyes of Britain is not consdiered a qualified teacher with QTS. This is also the case for all teachers who come from places like Australia, South Africa and Canada and the States...does not apply to those trained in the EU. When we come to teach in England, we can teach for up to four years and are considered (and sadly paid as) unqualified teachers, even though we are qualified in our own respective countries. Within those four years, if you want to remain teaching in Britain, you must obtain QTS, but there are a LOT of international teachers in this country who do NOT have it, and therefore the above quote proves as untrue, as qualified teacher yes, but not one with QTS!