Firstly I ran the autogen.sh script:
./autogen.sh --prefix=/opt/geany
then I ran 'make'. I then opened up a 'root' terminal and typed in 'make install'. The git repository was cloned to a directory under /home/xxx (ie $HOME on linux) and as per the above I wanted to install it to /opt/geany.
Then I tried to run the program with /opt/geany/bin/geany and it fails as per the above comments.