Inflatable Kayak

I rather fancy a kayak for our trips to Cornwall and other places, but I don't fancy carrying one on the roof. So I thought maybe an inflatable one.

Trouble is, most of the ones I've seen look a bit 'wobbly' when inflated - rather like a rubber dinghy.

When last in Cornwall, I saw a guy inflating one and when he'd finished, it looked more like a 'normal' kayak.....but he'd gone before I had chance to ask him about it.

Does anyone have any experience of these?