Cheers for the advice, always welcomed!
PracticalFishkeeping recommends a 48 x 18 x 18 for a single, which is what he's in now, BUT I had certainly planned for him to be in a much bigger tank later. At least double that (capacity not dimensions).
For the meantime he is only tiny, and the 4 footer seems like overkill at the moment. We've made two oversized caves, big enough for him to feel safe and shettlered while still letting us see him. He's allocated himself a territory underneath a 2ft long piece of bark. If the severums get to close he turns perpindicular to them and does a small dance to persuade them to think again, and he just snaps at the Geo (who is a serious bully).
When he's elsewhere in the tank he's polite and not a bully at all.
I will move the bristlenose with the severums when I do the change around, but can't until the Jaguar is moved on to a new home. Hutt Pets have agreed to take him on, so that's the plan at the moment. He's not as full of personality as I'd hoped, and if I use him as a way of getting rid of excess fish, he wont eat his pellets for two weeks or so (he is now). I think he'd be much better for an owner who feed live fish, which he gets very very very excited over.
If anybody wants a grumpy Jaguar let me know Good way to keep convict populations under control. Also a fantastic digger.