Toilet paper clogging the toilet
Usually the old toilets preformed the best due to not having to comply with water saving laws (at least here in the States). One way manufacturers conformed to the new codes was to (among other things)  narrow the throat of the toilet to increase the water flow to compensate for the decrease in gallons per flush allowed. But it sounds like the paper is getting hung up and caught somewhere near the toilet. Could be an obstruction(kids toy, toothbrush, pencil, etc.) just wedged in the bend at the toilet base or in the sewer drain under the floor. If it can't be plunged, snaked or augured you'll need to remove the toilet to visually check for obstructions. If there is a sink in the same room does the water drain normally? if so the blockage is directly after the toilet (in the sewer line) or inside the toilet.