alternatively, you can buy hydrogen peroxide off the shelf. im not sure if the 20 vols stuff is available for general purchase. generally the 10vols stuff isnt strong enough.
same as above, spray on leave for 10 mins and then heat up using either really hot water or a hair dryer etc...
careful on patterned wools as ive seem some real messes. also be prepared for texture changes in wool and the obvious colour / dye lightening.
thanks,
dan