Yes they will spray the door as well if you want it done well.
trouble is you cannot 100% match the colour and if the new colour finishes on the edge of a panel its almost always very obvious blending through the door makes a much nicer job.
Also think your estimates are quit low, I'd say £100 a good price to paint a wing if it was off the car and hey are simply painting it and handing it back to you. if you expecting them to fit it, stip the bits off the door, paint and blend I'd expect nearer £300.