Not done it on a Leon, but have done it on a mates Fiesta and my old car (MG ZR)
As above really. The pinch bolts on the hub/bottom of the suspension strut are notoriously tight on most cars. Get a decent breaker bar and you should be alright!
Get some decent spring compressors though. When doing my mates car for him, one of the spring compressors came loose and spun round the spring, trapping my finger, nearly taking it off. The next couple of hours spent doing the other shock were squeaky-bum time, as it really shook me up.
Don't let my horror story put you off.. i've heard a guy once lost 5 teeth when the spring hit him! ANy less than 5 and i'd call it a success.