i have tried most of the recomended sources out there. but i have finally settled on Gloss grey backed material from europoint display.
if anyone seen the stands i had at signuk, these were done using that material and i have done various work for customers using same, all very happy. the ones i had at signuk were about 48 inches wide and there was no curling at all and it had been printed using activasol inks.
oh, and an added bonus was it was cheaper than any of the others i had tried also… this is a new product for them, so if calling, be sure you are getting the right stuff. i was dealing with cameron steer of the glasgow branch.