I'm not saying anything, you were the one claiming there are CAA regulations prohibiting it.
If you can cite an article in the Air Navigation Order or other legislation that prohibits flying an SUA under 7Kg in the ATZ then provide a reference to it. I would be interested to see it.
Whilst I would agree with the BMFA that flying in the ATZ may be unwise they aren't an authoritative source and unwise is not the same as illegal.
With regard to your suggestion that you should fly at the end of the runway I suspect there are articles in the ANO, 137 for a start, that would prohibit that if the airport were open and traffic was landing on that runway.