I remembered, when i bought mine i made a little calculator in excel to work out APR. (Sorry, i'm a computer programmer, we do these things).
So I fed in the numbers from these deals to get an idea. Its not perfect as i dont know the exact numbers but i did a bit of trial and error. Here's what i got. Have to say, that looks like a great discount you have got! That said i'd be a little worried about that final payment, it looks on the high side, can't see you coming out of it with any equity.
Although i am assuming 0 trade in, which might be where my numbers are out and would make the final payment lower.
Ps if anyone wants my little finance calculator let me know and i'll email it to you!