If done correctly with suitable tools ect, the work can be done in a day. That being removal of old head, and new head in place. When I took mine out the hardest thing was the rear access to the EGR Bolts. First time I removed the head I took out the entire head along with both manifolds and turbo.
I think £200 for the job is a reasonable price for the labour, especially if it's a good mechanic.