how to stop my rabbit pooping and the odd wee on my sofa

Question
i have had my continental giant for a few weeks now he is really good messing in his litter tray, but no matter when he jumps on my sofa he does a scattering of poo then the odd wee how can i stop this.

Answer
The first thing that popped in my head is wondering if your boy is neutered.  Some rabbits are territorial messers and some rabbits will mark an area as their area with poop and/or pee.  And you haven't had him very long.  Sometimes, when I first bring a rabbit home, they will mark an area to let everyone in the house know they are there or that they claim that area.  Over time, that marking would usually decrease if they have been fixed.  

Now it could also be that he is one of those rabbits that will always leave a mess.  My first rabbit was really good outside his cage until he feel asleep, then he would leave a few droppings.  But the pee thing does make me lean more toward a territorial/not neutered issue.

You can also try restricting his access to the sofa.  Or try redirecting by placing a litter box in the room and filling it with hay or a favorite treat to encourage him to do his business somewhere else.  This article mentions a similar problem with someone having a rabbit using their sofa for a litter box:
http://www.rabbit.org/journal/3-12/litter-training-revisited.html

It also goes over some good housetraining tips.

Hope this helps