Torsion bar adjustment is covered in the manual. Its easy but you need to crawl underneath. Couple of 19mm spanners I think, and theres a locknut that needs loosening then just wind the adjusting bolt clockwise (I think? its been a while!) to raise it. But make sure you do same number of turns both sides.
Where are you measuring this 4" - top of wheelarch?
The manual actually shows the setup against a height differential between the inner and outer ends of the lower wishbone...thats not terribly accurate though so to compensate for any towing load, most people wind them up until the front wheelarch is about 2-3cms nearer the ground than the rears.
They take a while to settle (bouncing the suspension doesn't hack it I'm afraid) so needs rechecking 2-3 days after.