........ All sewer pipes leading from toilets are 100mm (4") pipe.[/QUOTE]
In the States, most jurisdictions require a 4" connection with a 1/8" per foot slope to the ultimate location of holding or disposing of the waste. If the plumber didn't do a good job of maintaining the slope or there are burrs in the pipe, that can cause problems with paper getting caught on them. Usually there is a vertical drop from the toilet into the waste pipe down to the basement and that is usually enough to keep everything flowing. Clogs are usually a result of something getting stuck closer to the water closet, such as a defective install of the wax ring. I do like the rubber collar that you use in Australia better, but I don't think that the code would allow it here..... at least not for a while. The code doesn't change very frequently when it comes to plumbing... slow to change, means slow to accept new ideas....