Sorry to read this sad tale Isee.
If my recent experience is anything to go by, the Exchange Scheme would have been detailed within the documentation provided to you by Lexus when you collected the car. In addition it has for some time been included in the Lexus U.K. website within the section referring to the purchase of a Pre-Owned Lexus vehicle.
Notwithstanding what I have said...you are where you are.....i.e. a dissatisfied Lexus customer and I would advise that you write to the Dealer Principal at Lexus Bradford explaining in as much detail as possible, what you have outlined in this thread. Provide as much information and contemporary documentations/notes etc and given that your current location seems to be far removed from Bradford, ask "if he would be willing for you to take the vehicle to your local Lexus dealer for it to be inspected and for them to comment upon the matters you have raised. Should they (your Local Dealer) support your views, and confirm the reasons for your current dissatisfaction, then you would expect the matter to be addressed by the LEXUS ORGANISATION to your satisfaction without cost to you"
I hope that this suggestion is of some use Isee.
Regards