I would just put the two up against each other. Where they meet - leave out the glass running down the back centre of one and remove the door of the other. This way you can walk through. Yes you will still have some glass inside but you would be able to walk right through. You can also buy some small metal brackets that would "clamp" the two frames together. Attach a strip of bubble wrap to close the join all the way round to prevent draughts.
Alternatively, stand them back to back with an entrance at each end. ;)
