I have the job of trying to remove the fittings for an existing soft-close, top-fix, toilet seat.
The problem is that I cannot get the 2 existing bungs and one stubborn machine screw out of the holes in the porcelain. The screw just goes round and round in the hole - it won't unscrew out and it won't tighten either, for that matter).
Is there a particular technique for removing:
(a) both of the rubber bungs and,in particular,
(b) a machine screw that seems to have its thread broken?
I attach 4 photographs showing the position as it is now.

I have already tried WD40 and have also tried applying pressure against the washer from under the screw whilst continuing to try to unscrew it from above, but without success. Someone previously suggested to me cutting the head off the screw but surely that would make the matter even worse as everything else would still be left in the hole.
I imagine this is not the first time someone has had this problem. Anyone got any ideas that might help? As a DIYer I have never come across these type of fittings before and do not even know what is actually inside the 2 holes in the porcelain - all I can see is some rubber at the top and apparently a metal thread deeper down.
Many thanks,
Dave
The problem is that I cannot get the 2 existing bungs and one stubborn machine screw out of the holes in the porcelain. The screw just goes round and round in the hole - it won't unscrew out and it won't tighten either, for that matter).
Is there a particular technique for removing:
(a) both of the rubber bungs and,in particular,
(b) a machine screw that seems to have its thread broken?
I attach 4 photographs showing the position as it is now.




I have already tried WD40 and have also tried applying pressure against the washer from under the screw whilst continuing to try to unscrew it from above, but without success. Someone previously suggested to me cutting the head off the screw but surely that would make the matter even worse as everything else would still be left in the hole.
I imagine this is not the first time someone has had this problem. Anyone got any ideas that might help? As a DIYer I have never come across these type of fittings before and do not even know what is actually inside the 2 holes in the porcelain - all I can see is some rubber at the top and apparently a metal thread deeper down.
Many thanks,
Dave