Mini spares do gift vouchers 
Thats what he bought me
That's the trouble with getting to your Dad's age - He will already have most of the things he needs and the things he might want are - generally - out of the reach of his offspring.
So, it all comes down to money. A track day session would be great (and they usually allow a second driver - hint) but that isn't cheap.
More affordable and something I always enjoy (and I suspect I am a lot older than your Dad) is something unusual in the food line. Dependent on his tastes, have an Indian or Chineese or Thai take-away delivered one evening. Just remember to tell your Mum first so you don't end up with two evening meals........
Bob
thanks for the ideas. I did have a think about some sort of track day, but I'm going to do that next year for several reasons.
I think any kind of meal would be wasted on him
If you're feeling really generous, buy him this... bit pricey though 
http://pistonheads.c...eds/4227801.htm
He's already got an elise and a billion other cars, he wouldnt have room even if I had the money!
It is very nice though!
just checked and saw that you are 18, do you still live at home?
trust me best prezzie you could give is to move out 
He left my mum before I could walk.. but I can understand why, shes a horrible women.