The common knowledge seems to be that the house robots are stored in a warehouse somewhere, the location of which is known by few people, one being Chris Reynolds, who was head of the BBC Visual Effects department at the time of Robot Wars.

I've never known him to be at any events; I'd imagine he's quite busy in his current work: http://www.alleffects.com/index.html

The only house robot shell that's been at an event in a long time is that of Sergeant Bash, appearing at Robots Live (not sure how many times) back in, I think, 2007.
However if you ever need some sort of house robot fix, Major Damage isn't too dissimilar to Mr. Psycho, and if you replaced its hammer with a circular saw, Battle Axe from Robots Live would be a dead ringer for Dead Metal