I'm sorry to hear about this, and yes it can be very annoying, but having said that, it is a very well published fact in most PC magazines and certainly in this forum.
Also when looking at websites that offer TFT monitors they also will advise you to read the disclaimer regarding dead pixels.
Although manufactures have a set guideline as to what is acceptable in the amount or position of the dead pixel/pixels, I think it also depends on the position on screen. If it is off to one side, or near a corner, then you are less likely to receive a helpful response than you would if it is right in the centre of your display.
Depending on this, why not give Evesham another phone call explaining the problem, and if you have just spent a considerable amount of money with them, they may take another look at your case.
Again if you are finding the problem so annoying, that it is completely spoiling your use of the new system and it is right in your line of view, then you may find Evesham more inclined to listen to a sympathetic appeal, rather than a demand for replacement.
Evesham do have a presence in this forum, and with a little luck may see this thread and make a reply to you.
Good luck with getting this sorted out, and if it is as bad as you say, I'm sure that Evesham will try to put matters right. J.