Roughly how much to install an additional radiator (not including the price of the radiator).

My new house has a large and freezing cold porch/hall. The new radiator will be within 6ft of the existing front room radiator.

Is it a simple job or am I being naïve?

From memory, we're paying about £100 a radiator, including buying the rads, but that's part of a new boiler install and on existing pipes so the system will be drained already and he'll already be on site, etc.