yeh, you have to undo one of the ball joints, i usually choose the lower one, not hard to do at all, i havent compressed the springs ever either.
1. take out the shock
2. undo the two swaybar? nuts on the bottom wishbone
3.remove split pin from ball joint and undo nut half way.
4. whack the wishbone/balljoint with a hammer until it flings down and sits on the half undone nut.
5. put a jack under the wishbone
6. undo nut fully
7.lower the jack down fully
8. get a nice screwdriver and hammer and wedge the spring off the lip its caught on
9. spring should fling down and stop on the ground depending on how high the cars jacked up, pull it out etc
ive never put standard springs back into a cortina, would imagine it'd be a bitch as compressors dont fit between the wishbones etc. lowered springs dont need compressing to get them in, and putting them in is the reverse order.