If you're British, not in jail, not sectioned under the mental health act and not the Queen, then there should be no excuse.
Go out and vote.
I'm not lobbying on behalf of any particular party, just on behalf of the democratic process. Even if you spoil your ballot - do something with it. Make it count.
People died for this y'know. And I'm not being funny - people, less than a century ago, actually died fighting for your right to vote. People are often complacent about it, seeing their right to participate in democracy as a given, but it's not. It's surprisingly recently aquired - for some more recent than others. Please don't take it for granted. Please don't think there's no point, or that your vote doesn't matter - if everyone thought like that then nothing would ever change or get done ever. It does matter, it does count, and it is important.
Also - it is my considered opinion that if you don't vote, you don't have a say in how the country is run. And if you have opted out of having a say in something, then your opinion of it obviously doesn't matter much. Thus I will be ignoring all coments and complaints about politics, and all political opinions from anyone who doesn't vote. If you don't want to make your voice heard, well, I for one will stop listening :) And if you want to complain about the electoral system itself, and how it's no longer fit for purpose, then there's still no excuse to sit on your hands - vote Lib Dem because they're planning on reforming it.