Haven't read all the above so may be repeating some of your responses but here goes:
-You must have owned the car for more than 1Year
-You must scrap the old car (must be more than 10yrs old) to qualify for the �2000
-the �2000 must go towards a new car
-The �2000 is and UP TO amount, not everyone will get the full allowance
-This offer is only valid between May 09 and March 2010
This is being offered because:
-new cars are more energy efficient and environmentally friendly, so govt wants old cars scrapped to get them off the streets
-Car industy is flagging, lots of cars and no one is buying. This will kick start the industry again.
Apologies if i have repeated any above comments, but the above is to the best of my knowledge (and also could be wrong, but I think that about the gist of it)