My roofrack lives on the car permanently. It's a Thule and has locks to stop you undoing the bars. Likewise the cycle carrier. I guess none would stand up to a determined thief but as a deterrent it's fine, certainly I've, so far, had no issues. All told, I guess what sits on my car must be worth about £400, I don't even think about it now. It probably helps that my car is a bit of a scruffy mutt and pig ugly, so people don't look twice.
I meant to add that because it's a little taller than most estates, I carry a folding step. Most of the time i don't use it but my wife does and it's handy for putting the middle bikes on. It means you don't have to lift the bike above your head until you are in a good position and then it's not as big a lift.