In reply to Philip:
Was in the same boat earlier this year and got a Thule Velo compact 3 (927 I think is the exact model), plus the extension kit.
Expensive maybe but it is total quality - I don't imagine I'll be selling it and it'll last a lot longer than 5 years. It hinges so you can get into the boot and both the tow bar attachment and the individual metal bars lock... whether you trust that is up to you. I use an extra cable lock if leaving them in a car park etc.
Currently it will carry two adult road bikes, a 26" road bike and a 20" Islabike.
Probably like you, I used to shove an MTB in the back of a KA then moved on to a Saris bones for three bikes but got sick of the faff of mounting it and it moving around. The Thule is utterly solid and easily the quickest option once its on the car. Heavy though and takes up a lot of space in the cellar!