I made these on Friday and they were delicious, also impressed the pants off my guests (not literally). I would concur with everything said above, I made 5, had enough cheesecake for 6 but only enough biscuit for 4!
The recipe says to pack down the biscuit base, but I suspect you dont need to do that, it might make it easier to eat later.
The rum is pretty strong, I will probably halve it next time I think.
Definitely worth a try though, its one of the easier recipes in the book.