I had been shopping around for suitably straight wood but the only unwarped, untwisted etc. wood I could find was speciality woods and they cost an arm an a leg.
I then settled on a few particle board shelves (typically used for kitchen cupboards and the likes) of which I bought 4. I laminated two together (with both glue and screws) as on there own they were a tad to easy to "distort". I then used these to make my bending brake from. It took a little while longer to laminate etc. but I'm very happy with the result.
It cost MUCH less than wood would'a cost (it's really expensive in South Africa), is solid, rigid and straight as an arrow.
I still just need to cut off the end of the one side to creat the overlap which serves as handles. My compound Mitre saw is unbelievably loud so I didn't want to fire that up at 12 o' clock last night. I'll do that this evening when I get home and then just add something to the inside to protect the skins.
Four particle boards lmainated to form two solid "planks"