I think that you will not get any change from £15000.00 to start with, and hopefully that will be that. But all I no is , as I just gone single, It will be more then that in the end. When You start adding all the little things just to make the car drive nice. eg more mapping,
maybe a new exhaust, to get more power, or just to be Quite, around town. new gauges,and we know how much they are, that is a easy £800.00 with out fitting. and then you got wheels and tyres ,you will need at least 285 on the rears , and that is £300.00 upwards , and then you got wheel arch rolling. And when you done all that, and the car is running at about 700 bhp. You might think about Fitting Nos , and thats about £1500 fitted , and before you know it you have hit that £20.000.00 .
But you will have a cracking car , and you will have great fun in it. just remember if you need to sale it . you will only see half your money back. That is the biggest joke.