Leave it as is. Buy a wide brim hat. Resist any urge to look up. There, advice I’d say…………
But more seriously, buy some lovely smooth flat plasterboards, any size you like except for plank. fix them over the curly swirly artex, carefully tape the joints……..then use a smidgin of joint filler applied to a smooth finish, and then merely pass a sanding block over. Decorate to suit and revel in a warm smug feeling…….