@ Mark
You make some good points, but the reason the authorities in the UK decided to set the upper age limit for 'indecent' images at 17 (whilst the sexual age of consent for males and females, gay or straight, remains 16) is a sop to the child protection industry, nothing more, nothing less. It was mandated and pushed for by the likes of the state-funded CEOP, who want to see their remit widened as far as possible, in order to guarantee work and funding as actual CP in the UK dries up and vanishes completely (see: IWF's own reporting on the actual figures for this).
The issue of 17 year olds being seen by UK courts as 'children', whilst the same courts also give them consent at 16 for sex with whomever they please at or over the same age (gay or straight) is the elephant in the room nobody - police, courts, politicians or media - seems to want to discuss or challenge.
Introducing completely fictional drawings, cartoons, CG imagery and the like into the indecency laws, equating them completely with actual child porn and pushing for the exact same penalties for possession, is an insult to rational thought, common sense and justice. CEOP must not be permitted to get away with this. A drawing (without any photographic content whatsoever) of a naked child, however explicit and in whatever medium, does not constitute child porn, no matter what they keep insisting - at best it could be seen as an offensive illustration, perhaps in very bad taste, but it is NOT child porn or child abuse. There is no victim involved, no child was harmed in any way and there is no defendant to appear before a court. It is a fiction cooked up by zealous advocates to further criminalise whole swathes of the population and it must be opposed all the way.