Oxfam festival volunteering - Anyone done it?

[SideWinder]

Just had a random idea of volunteering for Oxfam and in return I get a free ticket. They require a few shifts across the weekend (one in the day, one evening and one overnight) but otherwise my time is my own!

Not a bad selection either:
https://oxfamapps.org.uk/festivals/festivals/

https://oxfamapps.org.uk/festivals/information.php

Anyone done this before?