yes you should. Vote for the people you disagree with the least, or vote for the people who will thwart the party you disagree with the most. The choice is up to you how you decide to cast your vote but if you do not vote, you should not be entitled to make political statements in my opinion.
If you really cannot bring yourself to vote for an existing party then the only way you can get out of it in my eyes is to start your own party and vote for yourself.
People died so that we could have a democracy today and while it may not be a perfect democracy, we should use it or we will lose it. If we don't like the way a voting system is set up, maybe we should vote for another one that's better.
re: marijuana, what's happening is that in a couple of months our home secretary will hopefully sign a bill making cannabis a class C drug instead of a class B one. This will bring it down to the level of prescription drugs.
The first marijuana cafe in Britain will be set up the day after that bill is passed in Edinburgh, possibly on Cockburn Street, i will be along there within a week or two if it is allowed by the police to stay open. I haven't smoked any for a couple of years now, but i should like to lend my support to the concept. If that one is successful, you can bet that a few will open up in England, and maybe one in Glasgow too.