Chris - the problem with lock-ups is that I feel they are less safe in some ways than leaving your car on the raod. I had one a while back but they're so issolated, anyone can break in and nobody will see the criminals. At least on our street (Alma Grove) you can see your car, other people do keep an eye out for dodgy people, and it's easier to access.
I've found that lock-ups just end up being a pain in the long run. You can't get out of the car without banging the doors, you feel vulnerable when you park in them in the dark etc.