Problem with seat hinges

Here it is again;
https://www.choicereplacementtoiletseatshop.co.uk/c/spare-parts/toilet-seat-hinges

Things needed; set of johnnie bolts, wax ring, water supply tube, open end wrenches.
insert the flat head of the johnnie bolts into the groove of the floor flange so the threads are pointed straight up. Install the wax ring directly onto the floor flange. Set your toilet bowl down on top of the wax ring so the johnnie bolts stick up through the holes at the bottom. Install the washers and nut to secure the toilet to the floor. Depending on the type of toilet, you may or may not need to manually install the tank to bowl gasket and tank to bowl bolts. Set tank onto bowl and tighten the bolts. Usually a 1/2" wrench. Do not over tighten because the porcelain will break. Install the water supply to the bottom of the tank and then tighten it to the water shutoff valve. Install the seat, and your all set.

Install wax ring around base waste pipe. Make sure that 2 bolts are sticking out of a track under the toilet.Put toilet bolts through toilet holes and tighten nut with washer on each bolt to lock down the toilet. Now attache the water line that goes into toilet and bidet.

It is likely that the leakage is being caused by a worn-out flapper or seal (the part the flapper seats on). You can buy after-market kits that have replacement parts. What is the make and model of your toilet?

The hinges and bumpers on plastic seats are not replaceable. The bumpers are molded in and the hinges are installed with special tools while the plastic is still warm.
Sorry but that's way Bemis does things and is way most good Plumbing shops will not buy or sell them.
They were not like that untill they started having their seats made in China however this may help you http://www.bing.com/shopping/search?q=bemis+toilet+seat+replacement+parts&FORM=HURE


http://www.bizrate.com/plumbing-supplies/oid1620858646.html

need lock washers.

maybe by shortening the chain length on the flapper valve might help

it does this get used to it.

Any normal toilet seat may work, check your local Home Depo.