I had something similar to this in America, but couldn't find it, so I took a couple off here and combined them. I had great results with the 'scale of 1-10', because I had many bookings from a '2' on the scale, and people told me they would have checked No (or the equivalent) on the regular slip. This way I say "I see you have some interest in holding a party, what's keeping you from being more enthusiastic?" then work through their problem.