So why not resign and work as a contractor? Without wishing to be rude, it would seem that by your willingness to work for 20% of what others will, you're encouraging them to exploit you.
Thats something that i suggest to permies all the time when they complain about contractor pay.
very few actually do it, because they that its not as easy as they think it is.
As an example, I started work on a contract back in feb.. two weeks ago i was told the company had almost run out of money and might not be able to pay me... How many permies would accept that as a risk of their work?
As a plus side, i'm sat in bed readin el reg and watching daytime tv... cant complain. :)