I get about 400miles to £115, that's in a diesel X5
my 350z is even worse, but that's expected.
I don't think you're a million miles away with what you're getting. Most of the service iteam suggested won't make much of a difference to fuel consumption, but you should get it serviced anyway seems though you don't have any History
. It will help the engine last.
Providing the car is running ok, the only service item that can effect consumption a great deal is the air filter, if this is very dirty. Easy and very cheap to replace. Plugs and leads won't help unless it is missing a bit, or is hard to start.