I have the Dagger seat, which I bought off a friend for £30. It made things a bit easier, as it just slots under the foam, and bonding it down with a couple of patches evo-stick holds it in place, so converting back to a kayak shouldn't be too hard.
However, I have spent £20 on foam for the bulkhead, and I am still not happy with the outfitting, so I think I will be putting in some hip pads. The Velcro straps are crap, and so I will be after getting some webbing and buckles, which will cost be another £20. The strap positioning isn't very good in the kit, so I will have to drill some more holes and move the bottom mounting points. At the moment the top mounting points are using the holes left by removing the kayak seat, but I will be moving those back too.
If it wasn't for the fact that I got the kit cheap, I would probably have done it myself from scratch, or more likely never done it at all.