Not buy one and buy a proper sports car!! Z3's like Z4's are too sensible for a second car (unless he plays golf at the weekends!)... Tell him to get a Caterfield/Lotus/VX220. If hes a petrol head at heart, he will thank you for it i guarantee!
EDIT: Sod it, you can even fit a golf bag in the aforementioned's pax seat
Look for a late model 3.0 z3 - just got one for my wife and its great!! Got the sport seats, some fairly tasteful chrome bits and a proper mohair hood and all for £4900. It drives so much better than the 2.2 and 2.8 we looked at, the facelift back end is lovely and it is pretty quick and still sensible enough to use every day. Most of the fun of my 4 for a third of the price!! Bargain.
off to look at the silver one again today- it really does seem straight but this the first time we havent bought a car straight from the main dealer (and in dads case not brand new!) The car seems really genuine but is there any thing I realy need to look for or are there any big costs coming up with an 80k car? Help much appreciated so far guys.