Can anyone advise how you get the Planetary Shield and higher defensive building. I have gotten my research quite high but it does seem to give me the attack and defensive buildings each time I lvl up. My resource buildings give 10 units so have managed to plough quite a bit of research in this area

You research weapons and shields, and every 2nd one (usually) gives you a new structure.

And I had avoided researching them to concentrate on planets

Thanks

weapons, shields, and cloaks occasionaly give planet buildings on the 1st level of some of the tiers

likewise,... weapons, shields, defenses, and hulls occasionally give base structures on the 1st level of some of the tiers

see http://galaxylegion.com/wiki for more information