Rover 75 2002 Diesel Clutch Cylinder Leak problem?

Hi I have got a rover 75 2002 diesel....... about a week ago my clutch hit the floor whilst driving in busy traffic and I nearly fell off my seat. I had the car taken to my home address and as my dad has basic motor knowledge.......... I kindly asked if he would take a look at my clutch for me. We located the master clutch cylinder above the clutch pedal and topped this up with clutch fluid and located the bleeding nipple in the engine and bled the clutch or something like this. Any how after 4 days of driving the car the clutch hit the floor again now this process has been repeated a few times and my dad is getting sick of bothme and my car Lol........

Now I understand there is a possibility that it is the master cylinder or maybe the slave cylinder, with the slave cylinder being the more expensive option. Now I would prefer the cheaper option just like everyone else but how do I check which one is leaking as I can not afford to replace both of them if possible.

Please can someone suggest something practical...... my local garage is too busy at the moment and said once I have diagnosed or had the problem diagnosed they would replace it for me :-( what good it will be then I dont know?

Please please Help!!!!!

Thanks