Pete.
Here is the update....sounds like they should come out a lot easier when new.
Update.
It has become clear that its important to fit the bush with the correct orientation. That being with the void holes/slots nearest the front and back of the car, and with the solid areas, that join the centre spacer to the body, nearest the sides of the car so as to give most resistance to sideways movement, and allow movement for and aft.
Or as another point of refrance, if you look at the back of the bush ,or look from " the top" when viewed in its fitted position, you will see the 3 cut outs used for levering them out. One of the slots points directly at the centre of the bush, position this cut out nearest, or pointing at, the front of the car.
If the bush is not fitted correctly, the car will tramline and wander noticeably at the rear needing correction at the steering wheel. Note this gives no sensation of pulling through the steering, as the car is in effect steering from the back.
If you should need to reposition them, dont worry too much they come out alot easier when new and one even allowed me to force it back in with hammer! However the other was a bit more stubborn for some reason. Both sides re done in 1 hour. If only it was that easy first time round.
Hth.
So to reiterate, the solid sections pointing, or aligned with the rear dif. And the pointing along the line of the subframe arm.