[Dave at Pelican Parts]

If pumping the pedal makes things work correctly, you have air in the system. Period.

How are you bleeding the clutch? I am not familiar with the 1st-gen MINI, but I do know that some cars with hydraulic clutches can be difficult to bleed.

If you are certain that you have gotten all the air out, and the problem recurs, then you may have some kind of leak. Inspect the slave cylinder (if it is accessible), the master cylinder, and the lines for any signs of wetness.

--DD