Thank you all for your answers. The council have rang me today and asked me about it. I told them the job is so vile it would take at least £500 to get me over the threshold. They said okay. So that's how it stands, I get at least £500, more if it's even worse than we thought. I wonder what the other quote was, it must have been lots more for them to agree my price so readily. And you are right Martin I'll def need suits, shoes covers and masks.
I hope I've not been taken for a mug and will regret this.
Thanks everyone.