If something happens to a car in its first year of life, stolen, written off, most insurance companies will replace it for a brand new car but only if you are the first owner.
i think it only has to be less than a year old - also the small print often states subject to availability so its no substitute for a good GAP plan....
If zero lead time has real value for the OP then I would say go for it - on the other hand if they can wait a while then a new order will work out pretty much the same in real world costs and fee more special as its tailored to your specific requirements...
A lot of the insurance companies stipulate its only valid for the first owner. Yeah I suppose GAP would cover that gap

Also to the OP, you need to ask when it was first registered as that is when the warranty starts from. Some cars are registered then left in a yard for a while before being moved on.
Also the garage will have the V5C.
A lot of recommendations on the net saying you should leave with the V5C and not let them post it out to you
"t’s important to make sure you get your V5C certificate (logbook) as soon as you buy the car.
Some unscrupulous dealers want to hold onto the V5C for up to six months so they can prove to manufacturers that the car has been sold – something they can’t do if it’s in your possession.
If you agree to buy a car without a V5C, there are legal implications, including the risk that you the buyer could be committing a criminal offence when you drive the car. Don’t let dealers tell you they will post the V5C to you, either: the police and DVLA may want to see it, and insurers will need it to validate your car insurance policy or process claims.
What’s more, if the dealer you bought your car from goes bust before you get hold of your V5C, you could have a tough job proving that you are the registered keeper.
Our advice is simple: either leave with the VC5 in hand or walk away. Make sure you get a sales receipt and invoice too, as these prove that you legally own the vehicle."http://www.which.co.uk/cars/choosing-a-car/buying-a-car/buying-a-new-car/should-i-buy-a-pre-registered-car/