I started to take the oak toilet seat off, but it's always hard when
they use the standard plastic nuts to get a hold of them. This time
it's worse because the bolt is rusted, but using my fingers and using
a vice-grip pliers, I couldn't even start it turning.

Any suggestions?

I thought of using a soldering iron to melt through the plastic? ??
Should I use an electronics iron, which might make a nice thin cut, or
should I dig out my tincrafter's iron, used for gutters etc., much
bigger?

Are the fumes poisonous?

Is a socket wrench likely to fit? I'll have to hunt for my deep
sockets.

They sell tools for this purpose. I've seen two models.
http://www.amazon.com/Ginsey-Toilet-...ilet+seat+tool
http://www.amazon.com/Hertel-1-Toile...ilet+seat+tool
Worth buying?
The first one looks sort of flimsy and one rater said it was flimsy.
The second one was only 10.nn yesterday and now it's 12!