How does one remove the foreend from a Lee No. 1 Mark III enfield (without damaging it)?

You might try here.

http://www.surplusrifle.com/no4/index.asp

Rad

Take the barrel bands loose and remove the trigger guard and it should come off. Enfields are kinda modular built, but there's not much too them. Just start taking parts off and you'll get there.

NB to remove the butt you You MUST MUST MUST remove the forend! This is vital as the stock bolt in comes through the rear of the action to finish in a squared-off end. This end then is stopped from turning by a square metal lined recess in the back of your forend.

Step-by-step:

1. Remove bolt, magazine and rear hand guard.
2. Place rifle in vice upside down, gripped by the outer band. Muzzle to right. (CAN BE OMITTED)
3. Remove these screws:
Front nosecap screw
Rear nosecap screw
Outerband screw
Inner band screw, together with spring.
Front trigger guard screw.
Rear trigger guard screw.
4. Tap off nosecap.
5. Remove the trigger guard.
6. Take rifle out of vice. (IF STEP 2. TAKEN).
7. Remove the outer band.
8. Remove the front hand guard.
9. Tap off forend. Watch the stud and spring and put right hand underneath to catch them should they fall out.

I could go on, steps 10 to 17 to give a full strip and then some for bolt, magazine and backsight. But maybe not today!