X21 TJK said:
You should be able to. Are you trying to buy used ones on straight line HP? Ie, 36 x £600 a month = £21,600? You can get PCP (which includes a balloon on the end to bring down the monthly) on a Z4 up to three years old easily; this is the product you will have been quoted for by your dealership for a new one. Thus a cheaper, slightly used model will always be less than a new one, which will depreciate much more.
If you use a broker, he will also get you a much cheaper rate than the dealer too. Based on experience you should be able to get an 05/06 plate 2.5 Roadster with a good spec and under 10k miles on it for circa £350 a month....though I am not sure how much having a poor credit rating will knock this up - if it's to £600, I would lease one instead! Insane amount for a 2.5