Hi, as you've probably guessed by the title, I'm not brilliant at d.i.y, I've been through about 5 toilet seats, as they keep snapping, so I decided to get one from B&Q, seems a bit sturdier, but when I tighten it up, the stoppers at the front don't seem to quite reach the porcelain, when I push down on the front, it's forcing the back of the seat up and I'm guessing forcing the nut loose at the back, does anyone knoe how to rectify this? thanks