Or just buy a road worthy HGT for about £500.
There are a lot of differences in the brakes of an HGT much bigger and discs all round, the suspension is firmer and designed to carry the extra weight and performance. The gear box is different the electronics throughout the car are different different body computer and dial set up etc etc
By the time you've converted a 1.2 you could have bought a couple of HGTs without any hassle.