Clutch or master cylinder?

Ok people Here it is my clutch pedal he stuck a few time in the last. Month It stuck about 1inch down then springs back and hits my foot.
Well today I pulled away quit sharpish up hill and clutch
Seemed to slip. Going from 1st to 2nd and 3rd. Now I thought if it was the clutch it would slip all the time yet It does not it pulls up hill like a train and can stall easy. Would a fault master cylinder cause this or not?

sounds very much that the clutch release arm is sticking where it enters/pivots in the bell housing, copious amonts of wd40 or equivalent needed, or worst case dismantling to lubricate internal pivot of clutchrelease arm, check out also the slave cyl. bracketry, this can also fail.