Right guys! I have an update for you with regards to all this!
I took my Z back to the dealer today....I now have a two year warranty, all the issues will be fixed and the manager gave me his car until mine is fixed!
With regards to the 7k in 3 months, the manager phoned the previous owner and he said that he's done the full 7k. he said that for the last 3 months of owning my Z, he used it for work (100miles a day) so there's a genuine reason for those miles. also, the dealer had my car for 1 week before i bought it.
SO, lets see what happens when i get my Z back! hopefully it will have a happy ending and i can get on with enjoying my 350Z!!
Thanks for all your input guys! True legends here!