OK, so if i'm talking about flying home to Filton or Cardiff, which has class D airspace all around it, if the weather is poor, and i'm returning IFR, I can fly with a visibility under cloud of 1800m - same as I ever could. Now how about the decision height. Say I'm using the ILS - can I still go down to 500ft? As I say, the CFI says that I can't, but I would like to see it somewhere - it isn't an easy one to find.