Your problem might not be the rad at all. My 3A has the rad positioned upright behind the shocks and the front cross member. Its been like this for the 14 years i've had the car with no over heating problems. Are you sure that all the water galleries in the block are free from dirt and sludge etc? Also as Mick touched on earlier, the air not only needs to get in through the rad its needs to get out from under the bonnet. All you can do is work through things one at a time. We've all been there for one reason or another, keep asking questions and someone will answer. Also someone local to you may be willing to give hands on help. It's that kind of club.