We had a quote (which we were happy with) from a builder for some internal work, to remove a chimney breast. The builder seemed to think he could remove the chimney downstairs and support the rest. We accepted the quote and he gave us a date to start work.
I wasn't convinced about his plan so I asked him to come back to take another look at the work before starting to make sure he was happy and knew what he was doing. I also asked if he could replaster the whole ceiling to which he replied whatever you want love.
Once the work started, he realised that the chimney couldn't be supported and therefore needed removing in full. He said he could do the work for an extra £1k 
which we agreed to.
The work was done, with the exception of the ceiling replaster which was subsequently arranged for later in the week and
we were happy.
The final bill arrived which then included and extra £200 (on top of the agreed £1k). When we queried this we were told that this is what it cost??? There had been no mention of this £200 but he agreed to knock it off if we paid that day. Which we did.
10 days later, a bill has been dropped off now for he additional plastering. In all conversations there has been no mention of an additional cost for plastering. We would probably have got our own quotes for the work as it seems quite high.
We have tried to call twice this weekend to discuss it - I'm loathe to pay it as it's just been sprung on it but I would agree to pay half. Should we pay the full price?