Up and over doors are the least secure, easily bent or forced, reinforce the back of door with steel tubular bar.
Mortice locks to side frames,
Secure the roof, and windows, curtains on windows along with bars,
security lights,
Baby alarm if connected to mains and hiden, you can listen in ,
Covert cctv, so cheap now, http://www.cpc.co.uk
wall or floor anchors,
and lots more, but if they know your bikes are in there and they want them they WILL get in, avoid cleaning the bike outside if seen from the road, avoid leaving bike on car outside, or in car, dont advertise on any forum what bikes you have, even just putting up pictures, as its an incvite for someone to nick them.