Gas, Water heating and cooking options

Hi all, I'm looking for information, advice, experience etc on what is the best way to set up our heating and cooking options. We are building a 5 bedroom, three living area house. We have 4 children who are currently young but as they get in to teen years the water heating bill is no doubt going to grow substantially. We were initially going with gas for cooking, we have a point out side for the BBQ. We had originally thought of gas water heating but we are running off bottles in our area and have been advised at our plumbing selections to consider a heat pump for water heating as it should be much more cost effective. We have picked out gas cook top but we did this before the heat pump consideration came up. I'm just wondering if it is worth having gas just for cooking with? Have other people had this combo and found it works well and is cost effective? I am also wondering what the general opinion on Heat Pumps for water heating is? Thanks