I looked at doing something like this earlier this year. Fraser Cars basic kit starts as just ova 12K. Doesn't leave much at the top end of your budget to play with. You could also check out McGregor Cars. They are built here in CHCH so you could go have a look and a talk to the guy. From memory there kits are cheaper.
Almac in Wellington also do a cheap kit. IMO tho they look a bit cheap too.
PM me if you want the Fraser Cars Price list.