They are starting to get popular over here lately. On donedeal for €12.50 i think. I didn't buy any as of yet, but had a look on some sites from India, where there going for three or four quid a pop. That's some difference compared to eBay etc, where they are twenty to thirty quid for one trap.
As reguards the trap. It looks a good design, where a clean kill can be achieved from the front and sides. The design of the trap stops rats from getting at the bait from the back which is a bonus. Bait wise, maybe something like dog nuts would work well. Think it needs to be something solid like