yes any wear "thoughout" the mechanical system does tend to make some of the travel simply take-up the play instead of moving the clutch so try to re-new any worn bits as best you can
also (& i know this is difficult to check with-out removing it) check the master cyl is the correct one,,, so many these days are the .7 type,,, however,,, the .75 master cyl works much better & gives us more travel at the slave.
& yes my dad wrote an article to Leyland Aust (back in the day) regarding the fitting of the flat washer behind the throw-out bearing & they implimented it & sent out a letter to all the dealers suggesting this be fitted.
But an easy check is the arm,.,,rip it out & have a look at the bottom of it,,, the ball on the end should be a ball shape,,, not half a ball,,, the plunger that it fits into (or t/out carrier) can also be worn,,, these days nearly all of them are worn,,, not like the old days where these carriers were hard as rock & you would wear out 3 or 4 arms before you need to replace a carrier,,, now-days theyre almost all worn out & the new ones are simply not as hard
& yes while you have the arm out, you could almost bet that the clevis pins are also worn
re-new what you can see is worn,,, check the arm & carrier (they`re easy),,, but the master cyl is often a culprit """as well"""... & as much as i know it may seem a lot of work to do,,, i still reccomend, or suggest that you check it out,,, a .7 master cyl does not work anywhere near as well as a .75
let us know how you go
No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days
