Regarding the police action at Gosport in defining the whole of the town for section 34, I have to say this is far beyond the expectations of the law when it was discussed in Parliament.
It was supposed to deal with anti-social behaviour “centred on a particular locality”. The extent “should define a specific geographic location, for example by listing the streets to which it applies or the streets which form the boundary of the area”.
Parliament did not cap the area in section 34. It required a written, specified locality, and both the minister and the notes framed that locality as a particular place (a housing estate in the notes; streets or a bounded area in the guidance). A town wide authorisation is not forbidden by the section, but it is wider than the examples given when the extent was discussed.
As usual, though, when you give the police additional powers under law they will very quickly abuse them.