Close coupled WC

[klps]

I am trying to replace the plastic diaphragm on a close couple wc siphon. Naturally the siphon is a one piece cheapy version so I have to remove the cistern. The problem is that the two wing nuts are completely corroded. Any ideas?? I have tried WD40 however the bolt is so corroded that even if I managed to loosen it (which appears impossible), it would not travel much further. Hope this makes some sense

 

[ChrisR]

COUld try a slot cut across a piece of 15mm pipe to engage the wings.

Heating them often helps

Otherwise it's a hacksaw blade, unless you can get an angle grinder to them