Clutch Judder & Difficulty Going Down Gears

Model:Rover Mini Cooper
Year:1991
Description of problem:

I have searched though the other topics for clutch problems and have been unable to find something that matches the problem I am experiencing.

Recently I have felt a jump when changing up a gear, I can get round this by completely letting up on the throttle and then leaving a slight pause before depressing the clutch. I have also noticed that depressing the clutch can cause the engine speed to drop noticeably rather than just cause the car to freewheel freely.
When changing down it can be a bit difficult to get into 3rd or 2nd. 1st is usually ok.
I did read on the forum where someone suggested testing for clutch slippage by putting into 4th from a stop, reving to 2500rpm and letting up on the clutch. When I tried the car didnt stall but slowly crept forward which suggests it is slipping.
It is a verto clutch.
The slave cylinder was changed a few months back and there is no leak.
I have only had the car since June and it wasnt regularly maintained for a number of years so assume that not much has been replaced. I am also pretty new to vehicle maintenance.
Any suggestions gratefully received.

It could be the release bearing. It certainly sounds more likely to be a fault with the clutch itself rather than the hydraulics.

You could try adjusting the throw out stop. That’s the big nut in the middle of the clutch cover.