Following on from an earlier thread of mine ( http://www.vectra-c.com/forum/showthread.php?t=159604 ), which confirmed to me that most people had found that only the outer bush was worn on the rear upper control arms when they removed the old part, I decided to try and replace just the outer bushes yesterday, without going to the hassle of removing the arm from the car.
I used the "threaded rod and nut" method, which I've seen used on Wheeler Dealers, and in fact if you buy la-dee-da new bushes (e.g. ones with camber adjustment facility) then you sometimes get the rod, nut and a metal sleeve included with them. My bushes were from ebay, so I fashioned my own removal parts, i.e. an M12 threaded rod from Wickes and several nuts and washers.
This method worked a treat, and the outer bush was indeed totally worn - the metal sleeve inside the rubber could be moved up and down by hand, which isn't how it should be.
The shiny round metal thing in the middle of my bush removal contraption is an exhaust clamp, and it was used to pull the bush into it; the rusty metal thing to the right of it is an old dumbell weight, which has a hole small enough that the 32mm socket to the right of that doesn't slip through - the socket stops the washer on the rod from slipping through. If you had some bigass washers to hand you could do without the weight and the socket, but I didn't have any.
I reversed the tool to pull the new bush into the control arm afterwards, and job done.