Thank you for the reply, and I will be using R indeed so pvclust seems very useful!
So this would tell me how robust the nodes in the dendrogram are? Is there a way of carrying out hierarchical clustering but forcing the "cases" and "controls" into groups? If I have interpreted correctly, in this way I could use bootstrapping as suggested to generate a p-value and in my case show there is no good clustering between the two groups?
Are the heat maps on equivalent scales?
Yes all the data is one measure on the same scale.