It all depends on the claim.. if you want to pay £400 but then become messed about on payment, the courtesy car a Fiat Punto (if you even get one) and a nightmare from hell then the £400 is worth it.
Lexus are correct in what they are saying... but at least you will get a lexus Courtesy car and a real proper evaluation of your car if it was written off.
We have a good Insurance deal at the moment in the gold forums that will give you many benefits that Tesco have to offer.