My mate bought a Riot Air some time ago, it came with a power seat or something, thing is it has no backband just a solid inbuilt back rest wich when you lean back say for back deck rolls or stern squits, results in extreme pain and lack of control. Any ideas on the best way to replace the seat or make it more comfortable? cheers

Yes. That's the Powerseat. DragoRossi does one called the Testaross or \"race\" seat, becase the design comes from slalom racing.
The intent is to raise the seat off the hull about 5cm, providing more leverage over your ends and edges. Also, the solid back actually allows for more direct energy control from the paddler, thus more control over the boat.

BUT, they must be padded out for a custom fit to your own body.

I've used thin strips of minicell, about the thickness of a camping mat to wrap over the top of the back part, and down to right where my arse starts to be. Thus creating padding for my lower back, and a pocket to hold my butt down to the seat.
It takes some experimenting, but once you get it right, it really works well.
If it's still hitting you in the back, then you are having poor posture, and should concentrate on that to improve your boating skills too.

It's not for everyone, but those who can figure out the outfitting really see much benefit from the seat.

I have encountered problems with the Riot back bands. The new solid pannel back bands seem to work much better than what was in boats last year. That said it still needs some tweaking. I have taken one and put an extra Wavesport back band in that we had around the shop. I still had a problem because the available mounting points left the band to low still. If your torso height is different from mine though that fix may work. I know North Water does a band that may work as well with a cam lever in the back.

If the padding the seat doesnt work which would probably be the best idea contact peak uk and ask them if they have any seats for the air they may do but it is going to be quite expensive probably