I am led to believe it is a standard feature of many old Triumphs that the clutch doesn't disengage until you've got your foot pushed through the bulkhead.
You could try one of these:
http://www.ebay.co.uk/itm/MASTER-CYL...item5add9edd9f
I've got a pair on mine but I can't comment on what it does to the clutch biting point because my standard clutch master cylinder was leaking when I bought the car and I haven't yet got it running to see where it's at now.
I hope this helps.
