The #1 thing I use for Calcaneal Apophysitis is a Silicon heel cup. My preference is one made by Silipos, although many heel lifts and cushions will work. Depending on the severity, I will have the patient rest, use ice, take an anti-inflammatory by mouth or use topically.
As far as the 1 cm limb length difference, I do not know how significant it is. We are none of us completely equal on each side. I ahve seen patients with 1-2 inch limb length differences with no other problems and others with a 1/2" difference have a problem (sorry, I forgot you Aussies use metric measurements read 2.5-5 cm and 1.75 cm)
for further information do a search on Google for Sever's disease and anything else you might be concerned about.
Hope this helps