Thats very poor from Mill Hill, they should know better than that being one of the special performance centres. Although they may be getting a lot of interest to test drive these cars now (GTR too) where people have no intention to buy.
Do as Mike says, let them find you one, get it in, test drive it and walk away! I test drove one at a Nissan dealer with no intention to buy, they were just local and I wanted to see what the car was like. Dont go buying one with no test drive prior as you wont know if you like it or not. I did the same with my Leon too. Test drove one at Newbury, but a dealership up north were selling them off cheap, so when Newbury didnt price match, I drove 200miles to get it £2.5k cheaper! (new car - like for like with Newbury)