Thanks for that, mostly what I was after.
I've been chatting to him on the phone to get out of him what he intends doing. Basically when he gets a new boiler he intends using the old system, The outlet from the old electric cylinder in his loft, which is close to above his stove, is going to feed into his tank sat onto his log burner, this he claims is "half inch" and so will be ok. He also thinks that because he is connecting this to a vented system then that part is ok. he then intends to draw this off straight to a tap, again through "half inch" pipe to the kitchen.
As I said he can't think things through properly, when I pointed out this would involve two hot taps in the kitchen he changed the subject quick.
He is adamant now he doesn't need it approved or a hetas engineer, as the stove is already installed, all he is doing is putting a "tank" in his lounge not a "boiler".
I will print those leaflets out to show him.