In a moment of inspiration, I have created a dirt cheap easily removable rack for transporting 2 bikes upright inside a car. It's also usable as a rack outside the car as well
I reserved one of these from Halfords. I dare say you could probably find them cheaper somewhere else, but it was close by and seems fairly solid and not too heavy
Once I got it home, made some precision adjustments with a long handled mass accelerometer* to the width of the upright bars to accommodate fat MTB rubber and stuck it in the rear of the car, secured by a couple of bungie cords
Bungie length and position will depend on your car
Then, it was seat down on the bike (Reverbs are Sooooooo useful!), front wheel out and into the rack
Additional bungie added to bars to make the whole thing rock solid.
A good result of a total time investment of 45 minutes (which included going to get the rack!)
*yes, I ****ed it with a hammer