Has anybody built decking before with a curved edge / front / step?

Google images shows loads of lush pictures but there is no way of being able to recreate it with your standard b and q decking boards.

Best bit advice i have seen so far is to cut the thickness of a non pre treated board down to approx half and soak for a while. Then pin and glue the same as you would with a skirting board.

The steps however, no idea.

Any thoughts?

Depends on how curved you are talking about. You could make a series of spaced cuts in back of the board a bit like the Mdf sheets you can get.
Other than that as you suggest you are into steaming or laminating. I wonder if you could slice off the front third of the board and bond it to some exterior grade plywood.
We used to do a lot of soaking and pressing making skate boards etc but now tend to use flexiply for the curved shapes and helixes etc . but I don't think it would weather very well.

I saw a program years ago, a small boat building company was bending oak boards for the hull, they were using a conventional steam wallpaper striper, piping the steam into a massive plastic bag containing the board and I assume keep topping up the water every time it was required. I have no idea how long you would need to do this for until the boards were workable. It still looked a struggle to bend the board

David

I have seen it done wooden box big enough to take the deck board that you want bent, wallpaper steamer in one end and let it steam for about 30mins and wearing gloves fit it as quickly as poss as once it starts to cool not as flexible.

Unless you want/need a perfect curve I'd go for cut sections and a well built backing to screw to. Bending the (usually quite thick) boards will (I imagine) be hard work and they're likely to want to un-bend themselves over time too.

I built a square deck years ago in our garden with ratfers sat on bricks over a weed control membrane and then grooved planks screwed down on top. The edges are straight and screwed to the ends of the rafters. Still there and looking fine 10 years later although I have jet washed it before and soaked it with timber preservative to maintain the look of it and reduce the slipperiness when it's wet.

One tip I would give is to use decent decking screws so they don't rust and round off on the head. I'd also plan for a powered scredriver of some kind to drive them in - it would be hard work by hand!