Near-IR colour-colour diagram of near-IR nebulae associated with the CORNISH UCHIIs. The stellar contamination has been removed. Lower limits for sources visible only in H and K are also shown. The arrow shows the extinction vector, calculated using the extinction law from Stead & Hoare (2009). The predicted intrinsic colours of an ionised nebula are shown with a black triangle. The observed data and the intrinsic colours are shown in the AB magnitude system.