Hi Jase
I have got a Harrison kit which is made in QLD and have been very impressed with it so far , I havent had to do much cutting or grinding but that will depend alot on the things that you wish to do to your car and what you are prepaired to pay someone to do for you . Obviously it is always cheaper to do yourself . I would say the cheapest way to get a cobra is to buy one that is already done but where is the fun in that . Alot of guys here have the Classic kit that you mention and they are very pleased with them so it really is up to your personal preference on which kit maker gives what you think to be the best package .
here is a link to where i got my car from
Paul
http://www.cobrakits.com.au/