Just Me - This is from the FAO website. I guess it depends if your volunteering is to 'improve work skills'.

If your volunteering work is to 'improve work skills' then my reading is yes you would be eligible.

If your volunteering work is not to 'improve work skills' then you will need to do it for 15 hours per week to be eligible.

What is a work related commitment?
This is one or more of these activities:

paid work or self employment
setting up a business
training or studying
looking for work
voluntary work to improve your work skills*
Note: The time you spend in work related activities can be combined with other work related activities to meet the 15 hours per week requirements. Voluntary work that does not improve work skills cannot be combined with other activities and must be undertaken for at least 15 hours a week or 30 hours a fortnight.