That is a matter for your own conscience, hopefully you won't get shat on and require a Union to support you... mind you, it could be a valuable experience for you if you were.
As was pointed out somewhere the other day, Unions have to have a vote which gives a majority decision of all its members in order to take industrial action yet the Tory government claims to have the right to govern the country with a vote percentage of 36.9 % on a turnout of 66% !.... this is...
It's pretty pointless really, membership has diluted and most Union rules have been tightened to prevent Unions taking action. Where I work there are no union members and although probably staff are not banned from joining a Union there is certainly no encouragement in the form of awareness either.