Could be a hydraulic issue, have you checked your fluid level?
Both the DE and HR have slave cyl issues.
De slaves are external and HR are internal.
You have made no reference to how the clutch pedal feels?
Serves very little purpose and not an MOT requirement, so best to just remove and discard.
However, if you want a rust free one then I have a few in stock.
I run an HKS on my track DE.
Whatever you go for, make sure that it has a decent baffle set up.
If you are restricted for space then go for the longer type baffled sump.