This is where everything started:
http://www.sphsu.mrc.ac.uk/events/prison-health-symposium/
Scotland specific links:
http://www.policecare.scot.nhs.uk/
A number of important international links:
http://www.euro.who.int/en/health-topics/health-determinants/prisons-and-health
There is a Linkedin group for this network: