The 'car / van up against the door' routine doesn't work.
I know people who did that and all the thieves did was to break into the car, let the handbrake off and roll it down the drive.
A metal security post, anchored into the concrete that you can raise and lower would be better, as the theives would need the key or a (loud) electric cutting tool to remove.
Really sickening to hear that they tried to come again last night. They're obviously not pro thieves to hit the same place more than once in succession. Probably some local scrotes who want the bikes for themselves.
You could always purchase a paintball gun and stake them out one night......