I stumbled across this by chance, it's a survey regarding a proposed pipline being layed from Dorchester to Portland but it showns you all old military sites along the way!
Might be of some use to someone, enjoy!
http://www.mfa.gov.uk/environment/works/documents/statements/Isle-of-Portland/Appendix 3.4.2.pdf
Might be of some use to someone, enjoy!
http://www.mfa.gov.uk/environment/works/documents/statements/Isle-of-Portland/Appendix 3.4.2.pdf