Just to clarify -
Assuming that I had spoken to the airfield's owner and had been given permission to do so, and given that the airfield would be unlicenced (because it is outside its operating hours)
1) I would be allowed to practise glide approaches down to touch-and-go and would be exempted from the '500 ft' rule because I am "landing in accordance with normal aviation practice".
2) However, I would not be exempted from the '1500 ft' rule, so I would have to climb out to greater than 1500 ft if I wanted to circle around to try again.